White supremacists are obviously already inclined towards hatred and violence, but in other ways they are just like anybody else. They’re suggestible. They can be incited. They can take cues from political leaders and feel as if those cues grant legitimacy to their beliefs and actions.
So, when a Black Lives Matter protester gets beaten down and choked at a Trump rally and called a nigger and a monkey, and the candidate (who also happens to be leading in the polls) says that he probably deserved this treatment, it certainly seems like it could influence a few white supremacists to show up armed at a Black Lives Matter rally looking for trouble. Sending out racist tweets only strengthens this impression.
It’s really a matter of leadership. Trump has chosen to be the leader of a group that has a lynch mob mentality. I don’t think there is any doubt that he’s been encouraging and condoning this kind of behavior, even if he hasn’t told anyone to start shooting people.
I doubt he cares that things escalated to the point that five protestors got shot in Minneapolis, but he ought to.
Regardless, he needs to be held accountable for his rhetoric.