Additionally, there is a plan to implement a purge feature for particularly egregious posts, but as long as these communities are not allowed to spread their roots here, there shouldn’t be much of an issue. Seeing fascists and bigots getting whacked in the mod log doesn’t bother me much at all.

There’s nothing stopping them from setting up their own instances (like Gab did with Mastodon), but they will be ostracized from the fediverse.