It isn't popular, but they have a name and address right? Not talking violence, but the number one way of dealing with these sorts is to usually talk things out. If you're really concerned about, get a group of similarly minded people and make it unambiguously evident that this person is championing something a lot of people are not behind. It becomes much harder to ignore or wave off something when people start making themselves known on your doorstep.

And no, this isn't dog whistling violence. It is simply applying signal. The only other message I can think of is engaging an investigative journalist/PI and starting to figure out who is lobbying the person, and start pressuring them.