I believe you that Meta is a bad company with a clear track record of perpetrating harms any time there's profit to be made. I am not, however convinced that small independent services blocking communication with them is a net positive for the world. Instead, I think there's an opportunity to get their users to migrate away.
That's not to say that some servers shouldn't block them. For a tightly-moderated server, the scale of moderation problems it could bring is argument enough. There are good options for those who are looking for that sort of thing.
I don't want my Lemmy server to block Threads unless it actually does become a moderation nightmare. I don't intend to block it from my self-hosted Mastodon server either. In fact, I haven't blocked anything there yet. I will if I run into anybody being a jerk, but it seems like bird photos and flashlight reviews don't attract that sort of thing.