Over the weekend, activists descended on Berkeley, California, and attacked peaceful protesters. But it wasn't far-right white supremacists leading the violence this time, as was the case in Charlottesville, Virginia, a few weeks ago. It was left-wing "antifa" (short for "anti-fascist") counterprotesters who assaulted people.

The attack on peaceful right-wing protesters has once again invigorated debates over the use of political violence — discussions that go back to a protester punching white nationalist Richard Spencer in the face during rallies against President Donald Trump's inauguration. Such violence violates longstanding political norms in the US, and many Americans find any political violence deplorable — but it's now a topic of conversation nonetheless.

The argument for antifa activists is that the current crop of right-wing protesters — which are partly but not entirely made up of neo-Nazis, KKK members, and other white supremacists and nationalists — are so extreme that they must be stopped swiftly and even violently. Antifa supporters worry that if these groups' views aren't completely robbed of any kind of platform, they could gain legitimacy — and take advantage of democratic ideals like free speech to, ironically, promote their undemocratic messages. Violence is one way to get them off the stage.