If, like me, you’re an absolutist about the right to free speech, not just the legal letter of it but the stubborn spirit of it (as in: bring on the people I hate the most and let them speak, speak, speak until they’re blue in the face), then when you watch “No Safe Spaces,” a documentary about the crackdown on free expression that’s now taking place on American college campuses, you’ll find yourself, at least momentarily, in the company of some rather dicey “comrades.” People like the toxic fire-breather Ann Coulter, the everything-through-the-eye-of-the-Israel-needle right-wing ideologue Ben Shapiro, and — in a famously controversial and unsavory case — the loathsome alt-right showboat nihilist Milo Yiannopoulos.

All three of these moral reptiles, at different points, were invited to speak at public institutions of higher learning that wound up rescinding the invitations, due to pressure from their student bodies. And yet if you’re a religious believer in the First Amendment, then in “No Safe Spaces” people like Coulter and Shapiro become the de facto “good guys.” The “bad guys” are the students who, in numbers that are rapidly approaching 50 percent (according to a survey by the Pew Research Center), don’t believe that the principles of the First Amendment should apply to “hate speech.”

The problem with that view is: Who determines what is (and is not) hate speech?

And then, of course, there’s the thornier philosophical conundrum: Even if something is hate speech, why should it be banned? I hear hate speech all the time, some of it coming from our president. If you listen to right-wing talk radio, you can hear plenty of hate speech. Should it be banned? A lot of us — most of us — would say no. So why are our campuses, which are supposed to be about the free exchange of ideas, saying yes?

“No Safe Spaces” is a smart, vital, urgent, and provocative exploration of that question. Yet you may not be overly infatuated with the film’s messengers. Its two central figures are a pair of superstar radio personalities who have joined forces to become roving partners in the excavation of this topic: Adam Carolla, the comedian, actor, and former “Man Show” bad boy who is now a voice of prickly libertarian passion, hosting a podcast that is said to have been downloaded a record number of times; and Dennis Prager, the popular conservative talk-radio host.

These two come on, with maximum cheek, as strange bedfellows — Carolla the middle-aged bro of snark, a sports-car fanatic who still speaks the language of “the young”; and Prager, the cigar-chomping white-haired classical-music nerd who carries himself as a kind of post-Reaganite neocon grandee. As the two present themselves on their dual speaking tours, they have nothing at all in common…except for the issue of free speech. Actually, what they have in common is an affably unctuous attitude of glib mutual admiration. Yet they’re nothing if not articulate spokesmen for the impulse — the need — that human beings have to say whatever’s on their minds. And that’s a casual way of describing what free speech is.

In the movie, Carolla and Prager trade barbs and First Amendment arguments in their joint public appearances, which often take place at colleges — though in one case, they’re set to speak at California State University Northridge (where Carolla’s mother earned a degree in Chicano Studies), and the appearance gets canceled by the university due to the topic. On campus, it seems, you’re not allowed to talk about the lack of free speech on campus! There’s a sick Orwellian logic to that.

In “No Safe Spaces,” we see Barack Obama, speaking at a rally back when he was president, sum up the argument: “I’ve heard there are some college campuses where they don’t want to have a guest speaker who’s too conservative. Anybody who comes to speak to you, and you disagree with, you should have an argument with them. But you shouldn’t silence them by saying you can’t come because I’m too sensitive to hear what you have to say.” The pundit Van Jones puts it even more powerfully: “We’re creating this environment where liberals and leftists and progressives on campuses think that they need to get government authority or university authority to protect their ears from stuff they don’t like, or stuff that’s actually offensive, or stuff that is racist or is sexist or is horrible. And I just think that’s a very dangerous view.”

“Cancel culture,” a phrase that’s been applied mostly to the post–#MeToo world of mass entertainment, is part of what these controversies are about: students using, and feeling, their power to dictate who can be allowed in the public square. We see footage of the protest against Milo Yiannopoulos’ Feb. 1, 2017, appearance at Berkeley, when a thousand students gathered in a force that turned violent (there is much broken glass and fire). They succeeded in canceling his speech. Part of the rationale, as is often true in these cases, was the inflated costs of security. (Ben Shapiro was allowed by the skin of his teeth to speak at Berkeley, but it set the university back $600,000.) The security issue becomes a Trojan Horse for the clampdown on free expression.

I think Milo Yiannopoulos is despicable, but when the Berkeley imbroglio went down, I flashed back to my own college days, and my honest-to-God feeling is that if I had been a 20-year-old student, I would have crawled across that broken glass to see Milo Yiannopoulos speak. Why? Because in 2017, as a 32-year-old editor at Breitbart News, he represented an aspect of the consciousness that elected Donald Trump president. I would have wanted to know this scoundrel better — not just to read his words or to see him on YouTube, but to be in his presence, to experience what he means as a human being. That’s what a live speaking engagement is about. And it’s what freedom is about. Knowing the enemy, and having the right to hear him.

“No Safe Spaces” makes the case for why it’s actually healthy, if not essential, to be exposed to ideas you disagree with and even violently don’t like; it toughens the muscles, preparing you for the rigors of the world. Directed with engrossing multimedia verve by Justin Folk, the film mixes in witty satirical cartoons, like a superhero parody called “Social Justice Warriors,” and it mounts a compelling argument against the self-perpetuating psychology of victim culture. It also offers a deconstruction of how “safe spaces” on campus work, tweaking a generation that’s grown up with too much shelter.

But anyone who watches “Real Time With Bill Maher” has heard all this before. The most head-turning point made by “No Safe Spaces” is that today’s anti-free-speech radicals, who on many college campuses dominate the discourse, are going to be tomorrow’s leaders. The university has, in a sense, been a Petri dish for the winnowing down of the First Amendment. Unless this idea is fought against, it’s likely to spread far beyond the cloister of academia. And if that happens, it won’t only be about controlling “hate speech.” It will be about controlling your speech, just because someone else hates it.