> "Go somewhere else" isn't a solution when a plurality of servers agree to tolerate racist, sexist, or just plain obscene conduct.

You've said this, but didn't bother to give a reason. Can't you go to church even when the plurality of people tolerate porn?

> I'm also amazed that giving users control over what they see isn't an option.

so... you never actually used Mastodon? Its users do have the ability to filter content based on keywords, accounts or domains.