Of course those racist Nazis are a bunch of idiots, but how can you be surprised when freedom-of-speech focused tech gets used by them? www.theverge.com/2019/7/12/20691957/mastodon-decentralized-social-network-gab-migration-fediverse-app-blocking
Obviously, a few large instances dominate the user base for all practical purposes: kevq.uk/centralisation-and-mastodon/. And likely the network splits into hate-speech/non-hate-speech blacklist boundaries. And since the dominating closed networks will never lose user counts (???), the only instance that dominates will be the main hate speech one.
The flagship instance was mastodon.social and then in 2020 they closed signups for it and created a secondary mastodon.online.