Yiannopoulos gains his fame (and generous book deals) through stirring up controversy. He is a Breitbart editor who was permanently suspended by Twitter for encouraging the excessive trolling of actress Leslie Jones.
The Brit is currently on a college speaking tour. The tour stops have been marked by protest (all of which inevitably gains him more conversation and infamy, so it's probably counter to the protesters' aims, but that's another conversation for another time), and Berkeley was no exception.
Protest is protected under the First Amendment as free speech, which many colleges understand and uphold. But the protests at Berkeley swiftly grew violent as fireworks, rocks and Molotov cocktails were thrown by "150 masked agitators," according to the university.
Yiannopoulos's speech was canceled by the school in the midst of these demonstrations.
On Thursday morning, Trump tweeted about them. He said the university "does not allow free speech and practices violence on innocent people with a different point of view." His tweet ended with a threat: "NO FEDERAL FUNDS?"
Trump's tweet (shocker) is a bit of an exaggeration. Berkeley clearly does allow free speech -- that's why both Yiannopoulos and the protesters were allowed to speak in the first place.
The university only stopped Yiannopoulos's speech "out of concern for public safety," which inevitably includes the speaker's own safety.
It was also, presumably, not the university leaders who started the violence, but those "agitators."
Although Trump chose to speak out against Yiannopoulos's detractors, he has said nothing about physical and verbal attacks from Yiannopoulos's supporters at other tour stops.
Last month, a man at the University of Washington, allegedly a student, shot a man at protests who was described by friends as "a longtime anti-fascist and dedicated activist."
The shooter was reportedly there to see Yiannopoulous and had asked him for an autographed "Make America Great Again" hat after he lost his in protests.
During a tour stop at the University of Wisconsin, Milwaukee, Yiannopoulos specifically targeted a student who is trans during his talk.
He displayed her name and photos of her, used male pronouns and made fun of her at length to talk about his distress over the bathroom use debate.
The university chancellor emailed the campus saying he would "not stand silently by when a member of our campus community is personally and wrongly attacked."
The student reply-all'ed that email. She wrote,
It was not a case where you had no way of knowing he would do this. Quite the contrary: Milo has a supremely extensive, highly-documented track record of doing precisely this. [...] Free speech does not cover harassment, and that's exactly what Milo did to me. But hey, do email about hashtagging #UWMstandstogether as if that fucking accomplishes anything.
Trump did not tweet about these incidents.
Citations: Twitter Permanently Suspends Conservative Writer Milo Yiannopoulos (BuzzFeed), Berkeley: '150 masked agitators' ahead of Milo Yiannopoulos talk (CNN), Video Shows Moments Before Shooting At UW Milo Yiannopoulos Protest (Patch), Shooter sent Facebook message to controversial speaker at UW (AP), Alt-Right Troll Milo Yiannopoulos Uses Campus Visit to Openly Mock a Transgender Student (New York Magazine), Hate's Insidious Face: UW-Milwaukee and the “Alt-Right” (Overpass Light Brigade)