The violence that stopped Breitbart tech editor Milo Yiannopoulos from speaking at the University of California, Berkeley this week happened after some incredibly irresponsible statements by university administrators and local politicians.

Berkeley Mayor Jesse Arreguin tweeted that Milo’s “hate speech” was not “welcome in our community.” UC Berkeley Chancellor Nicholas Dirks said that the university not only opposed Milo’s views, but also his ostensibly harmful presence on campus.

Yet most of the blame must lie squarely with the rioters, who include Black Bloc anarchists and so-called “Antifa” (anti-fascist) activists, who exemplify the very fascism they supposedly want to resist.

These groups openly and explicitly declare their intention to disrupt public gatherings where conservatives — or, really, anyone they do not like for whatever reason — are scheduled to appear. They not only celebrate violence, but they come armed, masked, and prepared to fight and vandalize.

Were these groups merely showing up at events to protest — to express their views without silencing others — they would be perfectly entitled to do so. But lately, they have taken advantage of the timidity of the police — which they helped engineer, through their participation in the Black Lives Matter movement — to run amok, breaking up events and assaulting innocent people in full view of law enforcement officers and even the media. They are almost never pursued and never punished.

Consider this, from the Berkeley campus newspaper, the Daily Californian: while there were three arrests made Wednesday — two in connection with violence earlier in the day — only one of them was made by campus police at the protest itself, despite the violence. As for the city police, “[a]ccording to Berkeley Police Department spokesperson Officer Byron White, the city of Berkeley did not make any arrests in connection with the protests Wednesday night,” the Daily Californian reported.

The groups that showed up Wednesday seem to exist to prevent others from exercising their civil and constitutional rights of free speech and assembly. It is time to treat them the way that the Southern Poverty Law Center — before it busied itself with suppressing conservative opinion — took on the Ku Klux Klan. It filed a civil suit against the KKK under a theory of agency, wherein the organization was held collectively responsible for any and all of the crimes and civil rights violations its members committed in furtherance of its aims.

In this case, that would mean holding radical left-wing groups collectively accountable for damage and civil rights violations by individuals at any particular protest — whether of Milo in Berkeley or Gavin McInnes in New York.

An objection might be raised: these groups are judgement-proof. That is, they are just a bunch of kids with Twitter accounts. Unlike the KKK, which had a national headquarters that it was forced to hand over to a black woman because of a $7 million civil judgment over the murder of her son, there are no assets to seize, no institutions to shut down, no one financially liable.

Well, maybe. In at least some cases, there is a paper trail connecting disruptive protests to large, well-funded organizations. In October 2016, Breitbart News reported that the George Soros-backed Democracy Alliance had funded left-wing groups with “materials, food, supplies, stipends and bail funds to sustain and escalate their disruption of business as usual.” A document obtained by Breitbart News showed the Democracy Alliance taking credit for participating in the “uprising in Baltimore.”

It is well past time for the government, or conservative legal foundations, to pursue the donors behind groups that proudly and deliberately prevent others from exercising their civil rights. And it is time to shame them: the black masks of the Black Bloc and so-called “Antifa” activists should be regarded like the white hoods of the Klan — as the uniforms of extremist hatred.

Joel B. Pollak is Senior Editor-at-Large at Breitbart News. He was named one of the “most influential” people in news media in 2016. His new book, How Trump Won: The Inside Story of a Revolution, is available from Regnery. Follow him on Twitter at @joelpollak.