You can't, because you want a site that values free speech. But any site that values free speech is going to have to repeatedly answer the same basic questions on Crypto and Communism. It's going to have to repeatedly say "No, we're not trying to censor you because of chosen group X that claims to be innate, we're banning you because of actual crimes you have committed"

It's fine to argue about crimes in the sense of whether they should be illegal and whether people have actually committed them. At some point, you need to acknowledge that criminals will continue to argue their points, and that you either need to ban them or acknowledge that the same arguments will be repeated against them.