I had a conversation with a young activist today who argued that violence on account of the marginalized is appropriate because it is effective. Here's my take on that.
Non-violent discourse norms are a public good. The fact that you can go out and express your ideas without fear of violent repercussions is something that everyone benefits from. At the same time, everyone is incentivized to claim the right of free expression for themselves and deny it others. So there are two equilibria: The nice one, where we can express ourselves freely and we punish people who try to deny others that right, and the not so nice one, where everyone can expect violent repercussions for their speech.
Now clearly, there are some cases that are so dire that we must be willing to sacrifice our discourse norms for a greater good. Maybe, for example, violence used to suppress Nazi speech was justified in pre-third reich Germany.
Supporters of violence directed against speech will typically claim that their situation is sufficiently dire to justify their chosen means. Thugs will claim the same thing, though. One would expect that an intelligent supporter of violence would argue that speech norms, as important as they are, must take a backseat to the pressing issues of the day.
One would think that a legitimate and intelligent supporter of violence would go to great pains to signal to others that they are not just an ideologically opportunist thug. Yet such signals aren't very common, signals often go very much the opposite way, and derision and hatred is directed towards liberal speech norms.
What puzzles me is not that people behave in this way, humans have the capacity to act in deeply thuggish ways. What does puzzle me is that people behave in this way and expect to be granted the moral high ground. If you want to live by the sword, go ahead, I can't stop you, but to expect others to cheer you on requires a significant lack of self awareness.