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? https://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: https://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.