Simple solution is to let it resolve by itself with some govt help.

Most of the problematic content you've mentioned is also illegal (hate speech, defamation, minor porn, etc) in democratic countries. Simply report the server hosting that to its countries' authorities and the fediverse should be cleansed of it. I doubt there are many servers being hosted out of countries with mechanisms so broken that they'll allow unrestricted access to highly illegal/harmful things on public forums.

The threat of lawful persecution should be enough for deterrence.