I’m not familiar with this incident, but it sounds like there was one violent guy that showed up and attacked someone. Horrible, should be condemned.
Contrast this with the successful silencing of Yiannopolis who was planned to speak at UC Berkeley, and the about 150 or so violent extremists that rioted, attacked people, and terrorized downtown Berkeley for 5 hours.
Violence should not be tolerated, and free speech needs to be protected regardless of the content of the speech. There will always be those that want to silence speech with violence. But the forces on the left seem to have a lot more of those people, and they seem to be a lot more organized and well-funded.