My question is how do you police something like this?

What is the desired outcome? Policing isn’t done for policing’s sake. It is a tool used to produce a result.

I can’t imagine normal well adjusted people wanting this group’s members around them in polite society.

If that is the goal, jailing the people (assuming they can be identified) is how to police it. That is our tool for removing people from society.

if there even is anything to do other than be disgusted by them.

For the individual, gaining an education is the best bet. As the saying goes: Great minds discuss ideas; average minds discuss events; small minds discuss people. When you gain the capacity to think about the world yourself, you no longer worry about what other people are thinking.