A year later, the Black Lives Matter movement was born in response to the acquittal of George Zimmerman for killing Trayvon Martin. In 2014, Black Lives Matter leaders began to organize protests after a policeman in Ferguson, Missouri, shot and killed Michael Brown. And last summer, in an effort to force presidential candidates to address police violence and mass incarceration, Black Lives Matter activists began disrupting candidates’ events.

After some initial hesitation and defensiveness, Bernie Sanders, Martin O’Malley, and Hillary Clinton reacted to these disruptions by meeting with activists and embracing much of their agenda. Most Republican candidates ignored the protests as best they could.

But Donald Trump saw them as an opportunity. Asked last August about a Bernie Sanders event in which Black Lives Matters protesters spoke at length from the stage, Trump called the senator from Vermont’s response “disgusting.” He added: “That will never happen with me! I don’t know if I’ll do the fighting myself or other people will, but that was a disgrace. I felt badly for him. But it showed that he was weak. Believe me, that’s not going to happen to Trump.”

It’s no coincidence that Trump raised the specter of violence. The Black Lives Matter disruptions had been peaceful. But as Trump’s campaign took off in the summer and fall of last year, he began depicting entire categories of overwhelmingly peaceful people as a physical threat. Undocumented Mexican immigrants were potential “rapists.” Syrian refugees were “strong, powerful men” who might be a “trojan horse” for ISIS.

Trump’s supporters exhibit high levels of what political scientists call “authoritarianism.” Authoritarians are unusually fearful of disorder and favor simple, brutal methods of quashing it. As Amanda Taub has noted, “When many Americans perceived imminent physical threats, the population of authoritarians could seem to swell rapidly.” So by fanning popular fears of chaos, especially violent chaos, Trump wins yet more votes.

He does this, in part, by turning his treatment of the activists who seek to disrupt his events into a parable for how he would restore order in society at large. At a rally in Atlanta last November, an African American man began chanting, “Black Lives Matter.” According to various reports, Trump supporters responded by punching and kicking him while yelling racial slurs. Meanwhile, from the podium, Trump contrasted his response with that of Sanders’s. “You see,” Trump declared, “he was politically correct … I promise you, that’s not going to happen with me. I promise you. Never going to happen. Not going to happen. Can’t let that stuff happen.” Later on Fox News, Trump declared that, “Maybe he should have been roughed up, because it was absolutely disgusting what he was doing.”