I don't think it's fair to blame 'liberals'. The University which expressed differences with the invitee's beliefs but invited him to speak, struggled to create a safe environment but ultimately was unable to do so, yes. They could be described as liberals. But violent protest is pretty much by definition an illiberal activity.

For example, would you describe the Black Panthers liberals? Personally I wouldn't. They may share some objectives with liberals - equal treatment of a minority - but methods matter. I would no more call those rioters liberals than I'd call white supremacists 'conservatives'.