This conversation has been going on Mastodon for a while now. The problem kind of boils down to the following: there are people who think Meta is a bad actor and having the literal entire rest of the fediverse defederating is the best way of dealing with that. And there are people who also agree that Meta is a bad actor, and think that partial defederation is the best way of dealing with it.

Its really hard to come (read: impossible) to come to a consensus on this, because part of the argument about what is a better tactical approach depends on knowing how Threads implements things like account portability, and this is currently unknown. Most people even assumed that Threads would not implement this at all, but Adam Mosseri just announced that this is an important feature, so who even knows.