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They've been maced by police, surrounded by yelling counterprotesters, and ordered to leave town — yet the white nationalist movement has vowed to continue rallying.

And experts say that, despite the opposition, the vitriol displayed over the weekend in Charlottesville, Virginia, may actually spur membership in hate groups.

Hate has many psychological roots, including lack of exposure to different types of people or dislike of a characteristic within one's own identity, experts say. But when it comes to deciding to join a hate group, receiving implicit permission is a large factor.

Watching a hate group rally or reading members' comments online can enable that.

There's been an uptick in hate groups over the past couple of years, according to the Southern Poverty Law Center, although the organization tracks them on a yearly basis and does not have data on whether there are increases after individual events like the Charlottesville attack.

Battle lines form between white nationalists, neo-Nazis and members of the "alt-right" and anti-fascist counter-protesters at the entrance to Lee Park during the "Unite the Right" rally in Charlottesville, Virginia, on Saturday. Chip Somodevilla / Getty Images file

But Heidi Beirich, who publishes the Southern Poverty Law Center's Hatewatch blog, said hate is spreading faster than ever.

"There's so much proliferation of hate propaganda with the Internet," she said. "And that is adding to the problem."

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White supremacy, in particular, has gained speed since Donald Trump announced his candidacy for president, she said.

"We've seen hate rallies and events well-attended in a way we hadn't in the few years prior," she said.

And Trump's choice on Tuesday to blame "two sides" for Saturday's violence — rather than to specifically blame white nationalism/supremacy — could have "a serious emboldening effect," said Peter Simi, an associate professor of sociology at Chapman University in Irvine, California, who studies far-right hate groups.

"He's now really gone farther than anything else he's done in terms of reaching out to these folks," Simi said Tuesday. "It's at least an implicit sanction of these rallies.

"They were already planning more, but they've basically gotten the seal of approval from the highest office of the land, and I have to imagine it feels pretty good for these folks," he said.

Much of hate is based in fear, said Dr. A.J. Marsden, an assistant professor of psychology at Beacon College in Leesburg, Florida — "basically, fear of the unknown, fear of what might happen and fear of anything that's different than you or falls outside your definition of what's supposed to be normal."

"We establish ourselves as a tribe, and we say this is the group for which I have a love for, for which I identify with"

Marsden cited Islamophobia as an example.

"There's a lot of hatred in the United States toward Muslims," she said. "One of the reasons is they don't understand the religion. ... There's a lot that they don't know, and that scares them, because there is a small part of Muslims who are violent, and that is what is driving the hate."

That concept is known as the "in-group/out-group theory" — the idea that people tend to define themselves in social groupings and are quick to degrade those who don't fit into those groups.

Related: Trump Says 'Alt-Left' Shares Blame for Charlottesville Rally Violence

Another concept that leads to hate is the projection of internal insecurities on other people.

"We've found that, especially when it comes to homosexuality, people act very homophobic and aggressive because, deep down inside, they're afraid that they might have a little bit of that, too — so they're projecting their hate onto other people," Marsden said.

Brian Levin, director of the Center for the Study of Hate and Extremism at California State University-San Bernardino, said news coverage of hate groups exacerbates the problem.

"Rallies like Charlottesville and the concomitant coverage both in news and social media is a boon to hate groups who seek two things: brand exposure and the promotion of their members as both victims and warriors standing up to a Goliath that threatens not only them, but white identity, culture and nationalism," he said.