Yea, exploding heads made the rounds a couple of times, but after actually checking them out it became clear it’s run by a teenager surrounded by other 10-15 teenagers. A few main instances blocked it and it died. The main teenager then started hilarious chaos as a whitelist-only instance, but because it did not attract anyone - federation was reenabled at some later point.
There’s a difference between a couple of edgy teens and a big set of ideological morons who keep causing trouble.
Defederation is a nuclear option - at the time user-level blocking was not a thing; nowadays it’s not a problem.
TL;DR - freedom of speech as much as possible, with limits when it becomes necessary.
Look, ma, we’re famous!