The only real answer is for everybody else to just stop showing up and stop reacting.
They're already generally relegated to a spot away from the actual event. If NOBODY showed to up protest their protest, and if NOBODY showed up to record and broadcast their presence, or even existence, then they would gain nothing and slowly fade away. It would be just a half-dozen nutjobs on a street corner with unnecessary police protection... and even that police protection would disappear in short order.
Unfortunately, we don't have that kind of self-restraint ourselves. They will be around as long as we encourage them.