Julia, a writer who lives in the San Francisco Bay Area, talks about the street-protest scene in Berkeley, Calif., this spring as if she had entered a war zone. “There are explosions happening everywhere. People are fighting. You’re not entirely sure who is an ally, who isn’t,” she says.

That’s part of the reason she won’t give her last name, since she fears that she will be targeted, harassed or doxxed like so many others who have had their identities attached to the blowups here. For a few days, the city’s mayor, Jesse Arreguin, even had to get himself security because of the threats he was receiving. “Our city is not going to be turned into a fight club,” he says defiantly, though no one is quite sure in this city of 121,000 long known as a test bed for the First Amendment.

As the far right and far left have clashed here over what kind of speech is permissible, Julia has tried to stake out new space created by the recurring violence. She helped found a group called Pastel Bloc, whose members wear disarming pinks in the streets as they provide water and support to other “antifascist” activists who might be engaged in more disruptive actions. Think of it as sort of a medic crew with fairy-dust slogans like “Resistance is Magic.” Anything to fight the growing sense of dread. “It’s getting scarier to protest,” she says.

The mosh pit started months ago at the city’s famous university campus, where militant left-wing activists “shut down” conservative provocateur Milo Yiannopoulos in February, setting fires, breaking windows, causing a campus-wide “shelter in place” order. Invited to speak by the Berkeley College Republicans–who have since filed a lawsuit against the school–the professional troll and self-described “dangerous faggot” never made it onto the stage. And as the story became national news, Berkeley again became a theater where a bigger battle over the rights and limits on free speech, dissent and respect all played out.

At their worst, the scrums have been belittling and violent, as grown men and women shout, punch and taunt one another or destroy property. But the questions many are fighting over cut to the core of the American democratic system. In a time when politics have turned toxic, are there ideas so repugnant and dangerous that they shouldn’t be allowed to be uttered in public? Do certain words amount to attacks and therefore justify violence in return? Or must all communities endure the speech they hate most, even when the point of the speech is to make others angry?

These are centuries-old debates, and freethinking Berkeley has seen countless protests over the decades. Yet city and university officials also say there is something unprecedented happening now. While some locals have shown up with the standard placards and megaphones, others have traveled from afar, bringing smoke bombs and sticks, seemingly spoiling for a fight. In three big clashes this spring, dozens have been arrested and others have been sent to the hospital. “This level of political violence is something we have not seen before,” says Arreguin. “This is a new situation.”

And there are signs of it elsewhere. On May 29, the mayor of Portland, Ore., asked federal authorities to halt upcoming “alt-right demonstrations” after two men were stabbed and killed while trying to protect young women from a man yelling anti-Muslim slurs on a commuter train. The suspect in the stabbings entered the courtroom for his arraignment on May 30, casting himself as a champion of the Constitution. “Get out if you don’t like free speech,” he declared. The mayor had another message. “There is never a place for bigotry or hatred in our community,” said Ted Wheeler, “and especially not now.”

Many on the left say the words free speech are now being used as a cover for spreading hate in America. Many on the right say the left has been reacting violently to mere words. And in an era when Americans feel tense and divided, some groups have zeroed in on Berkeley as “a stage for open melee,” as one conservative organizer put it, treating the town like a shrine to be captured or defended in a religious war.

Yiannopoulos, for his part, has promised to return to Berkeley for a “huge multiday” event later this year. “Free speech belongs to everyone, not just the spoilt brats of the academy,” he wrote on Facebook, promising to dedicate each day of the event to a different “enemy of free speech, including feminism, Black Lives Matter and Islam.”

There was a time when it appeared the spring confrontation could be avoided. Weeks before Yiannopoulos’ planned appearance, scores of professors begged the university to cancel it, saying in a letter that he espouses views they find deplorable–“white supremacy, transphobia and misogyny”–and that he crosses a line by “actively inciting” his audience to harass people. At a previous stop on his campus tour, in Wisconsin, Yiannopoulos mocked a transgender woman who had once attended the school, while projecting her photo as she sat in the audience. And there were swirling fears that he would publicly target undocumented students at Berkeley, having promised to use the event to launch a campaign against “sanctuary campuses.” (Yiannopoulos, who has said he’ll “never stop making jokes about taboo subjects,” says he was never going to single out students and describes the characterizations in the letter as “lies.”) University officials criticized his “odious behavior” but said none of the concerns justified denying his right to speak.

Others in the community, however, disagreed. As dusk fell on Feb. 1, hundreds of protesters gathered peacefully on Sproul Plaza, where students launched a movement for free speech in 1964. Then things got hostile. “All of that changed, radically, when into the middle of the crowd marched–and I mean literally marched–100 to 150 individuals dressed in black from head to toe,” says UC Berkeley spokesman Dan Mogulof, who was in the crowd.

It’s not clear how many of them might have actually been students, but some marchers did identify as “antifa”–short for antifascist–activists known to use “black bloc” techniques to hide their identities as they protest en masse. With bandannas wrapped around their faces, the group tore down barricades, shot projectiles at police and lit a light stand on fire, causing more than $100,000 worth of damage. After the decision was made to cancel Yiannopoulos’ event for safety reasons, some protesters spilled into nearby streets, crushing the front windows of bank chains, while other protesters cleaned up after them. Mogulof describes the black blockers as “highly disciplined,” and says the display is “something we had simply never seen here.”

Antifascist protesters have been showing up elsewhere. A woman allegedly shot one in Seattle while he was protesting another Yiannopoulos speech, and others hammered out limousine windows in Washington, D.C., on Donald Trump’s Inauguration Day. While voices from all over the spectrum criticize the destructive methods that some of them use, antifascist groups also say that they’ve seen upticks in interest since the alt right has gained momentum, and people feel that “you have to take a side,” says Shanta Driver, the national chair of the antifascist organization By Any Means Necessary.

Some antifascists who have been protesting in Berkeley–including many who embrace anarchist ideals of fighting government, capitalism and any form of hierarchy–say they have been unfairly labeled as agitators by the media. Many also defend methods like property damage as a lesser evil, justifiable in the face of “dehumanizing” speech. They contend that the “real violence” is spreading hateful ideologies and that shattered glass is “visual” protest. “That form of protest is not meant to look good. It’s not meant to be diplomatic,” says Louise Rosealma, an antifascist and anarchist who got clocked by a white nationalist protester, an incident that was recorded in a video that went viral. “It is meant to physically disrupt and shut down things that need to be shut down immediately.”

Even for those who believe that broken windows or censorship can be justified, it’s hard to decide which expressions can be reasonably called attacks and who deserves to be silenced. Some draw the line at advocating genocide or ethnic cleansing. Some draw the line at burning a cross on a front lawn. Some draw it at telling college students how to report their undocumented peers. Some simply say, “Free speech does not mean hate speech.”

Others believe that the line drawing has gotten out of control, especially when people are demanding that a public university censor some speakers but not others. Naweed Tahmas, a Berkeley College Republican, says one of his liberal peers told him that the phrase build a wall is offensive hate speech. Another told him that hate speech should be banned from Berkeley. “Of course there’s some courtesy you should take in speaking, but what they’re trying to say is the government should restrict certain types of speech,” Tahmas says, “and that’s a slippery slope.”

While many protesters on the left saw forcing Yiannopoulos from campus as a success, many on the right saw it as a call to action. Among them was Rich Black, a libertarian grant writer from the Los Angeles area who decided to organize a “comeback” in Berkeley, an event where right-wingers could “come and speak, from start to finish, without being physically shut down. That was the whole goal,” he says. Then, at least in some ways, things spun out of his control.

Black helped organize rallies in Berkeley’s city center to defend free speech in March and April. And the optics of the setting–a deep blue town where the city council has, for example, called for Trump’s impeachment and decided to boycott any companies that help build his proposed border wall–proved to be catnip. Groups spread the news on 4chan, Reddit and alt-right forums. While some conservatives came just to show support for Trump or to hear speeches, Black says, others showed up to provoke the left in real life.

“That’s what’s sad about these events. They really attract the worst of the worst,” Black says. “There is a huge faction of the right that is just like the left. They deal in absolutes. They’re outrageously angry. They need an excuse to relieve a lot of that pent up aggression.”

At one rally in April, an anonymous donor paid to fly a sign behind a plane in the sky: “Don’t take the bait! Rise above the hate!” And at least one assembly this spring ended with no one hurt. But multiple meet-ups turned ugly. Police confiscated knives and bats and pipes. Some were bloodied, some were trampled.

Mayor Arreguin insists that any people who came to fight were not from his town and feels the city has been unfairly tarred as a place where people can speak their minds only if they’re liberal. He doesn’t have kind words for the “extreme” groups on either side. “Words are different from fists and bats and large wooden sticks that are bloodying people,” he says, “and I certainly understand that people think certain words are objectionable and abhorrent and should not be tolerated, but we live in a free society.”

Such principles are often cast aside online, where disagreeable ideas are routinely met with anonymous blowback. Mayor Arreguin had to take on the security detail after he criticized Yiannopoulos on Twitter and received violent threats via social media, email and phone. Black, the right-wing organizer, says he’s gotten so many promises of physical harm from the people at either end of the spectrum that his new advocacy group, Liberty Revival Alliance, has considered hosting events “against the alt right.” After the video of her being punched went viral, Rosealma says not only her address but also the addresses of her parents have been spread on the web, along with pictures of her as a child. Threats of rape have poured in.

Back on campus, the Berkeley College Republicans tried to host other conservatives this spring–David Horowitz and Ann Coulter–but both events were canceled.

The club says there were too many administrative roadblocks and filed a lawsuit alleging that the university effectively acted “to restrict and stifle the speech of conservative students whose voices fall beyond the campus political orthodoxy.” The university has responded that cancellations have been related not to political views but to safety concerns that arose in the wake of the Yiannopoulos event–leading to more complicated logistics. A spokesperson says the school will keep pursuing the “delicate balance” between keeping people safe and upholding the First Amendment. The suit remains ongoing.

The university does not deny that the College Republicans have been having a hard time on campus. Tahmas, a 20-year-old rising senior studying political science and a member of the club, says when he and other members have set up their tables to attract new recruits, students have repeatedly torn up their signs or spit on them. On one occasion, he says, students poured drinks down on them from a building above. “We’re constantly harassed,” he says. “They are projecting stereotypes onto us, which are not true, and they’re also projecting their worst fears upon us. They believe we’re oppressors.”

Yet while some students may still be furious with the Berkeley College Republicans for inviting controversy to the campus, Tahmas says that their meetings were also better attended by the end of the semester. Newcomers “are not necessarily Republicans either,” he says. “They’re just interested in hearing us. Because the more you attack or attempt to silence a viewpoint, the more people are interested in it.”

That is a truth that the nation’s founders understood when they enshrined a protection for minority viewpoints in the Constitution. But there is growing confusion about where that protection now starts and stops. Tahmas says he’ll be ready to put out the table again come fall. “We’re going to keep going out there every day,” he says, “fighting against political correctness.” And others will be ready to literally battle over such ideas.

This appears in the June 12, 2017 issue of TIME.

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Write to Katy Steinmetz at katy.steinmetz@time.com.