If that was the argument presented I doubt there would be any argument to begin with. Saying ‘hey, you might not want to break connections with site for no reason so your users aren’t surprised or worry that they…so on and so forth’ could be met with a ‘hey, thanks for the advice’ and everyone would have moved on. Accusing them of censorship and attacking someone else’s freedom of speech because you don’t think a personal decision they made was justified because other people utilizing their platform expected something else is a completely different animal.

The onus is on the user to keep track of what the instance they're on is doing. Beehaw behaved in a manner that I don't agree with, so I chose not to sign up there. Lemmy.world has so far defederated from instances I would also choose to defederate from. If the admins ever start defederating willy-nilly without good cause, I'll choose another instance.

I do also think that there needs to be a certain amount of built-in stability in order for federated communities to grow.

I would argue that the Fediverse is inherently more stable than other platforms. The big platforms are defined by inconsistency. If you don't like it, you can take your ball and go home and that's your only choice. The Fediverse lets you take your ball anywhere you want. You don't even need to change apps