You agree then, everybody chooses not turn away and not listen to his hateful garbage and then somebody makes an (implied) threat of violence to the Nazi by angrily saying “Now sit down and don’t open your mouth again!”.
Is that what the guy was doing in the scene? I have watched that movie many times. The character that said that line is not at all violent. I don’t think he was threaten violence against the bigot. He just wanted the guy to sit down and shut up.