1st, violence absolutely is a political tool. That's the reality of the physical world we live in, and it's acknowledged in the 2nd amendment. Violence is a terrible thing and we should avoid it as much as possible. Unfortunately, our society has conflated not talking about violence with avoiding violence. Talking about violence and it's outcomes is one of the best ways to avoid violence.
2nd, calling for violent revolution is political speech covered by the 1st amendment. Debating these ideas publicly with SPEECH is much better than exchanging bullets. Universities SHOULD be a place where these ideas are discussed.
Obviously I disagree with all these people. But squashing debate doesn't stop the idea.