That was sort of the issue, was it not? Trump had the chance to properly denounce them and instead decided to leave an intentionally ambiguous message to avoid losing their support. Mentioning the group wouldn't be an issue if Trump would've simply condemned them.
What specific "violence" are you seeing from "Proud Boys"? As far as Antifa goes - Eric Clanton was protected from prosecution - tried to murder several people publicly in separate incidents and got off with probation. Are the prosecutors members of his group? Why not?