In my experience these "containment" boards/servers/sections tend not to work.

Long term it basically just creates a place that attracts those you don't want, and becomes place for those ideologies to spread. Then it either gets bad enough they take over (you know the site) or they break off wholesale and form a new community dedicated to those worst impulses (pyrrhic victory at best).

The best policy is to actively moderate, and in the case of the fediverse, defederate, those groups and those that give them shelter.