What I'm not sure on is the effect of making a community smaller. If you have 10 million people in a tepid cesspool, shutting down that cesspool might make 100

What I'm not sure on is the effect of making a community smaller. If you have 10 million people in a tepid cesspool, shutting down that cesspool might make 100k of them move to a more extreme location, while the remainder stop being exposed to that influence. The remaining smaller community is more extreme, but primarily because it has only the more extreme members of the previous iteration. Sort of like how doomsday cults get more fervent with each incorrectly predicted apocalypse. The cult gets smaller, but those that remain are the true believers.