that would be censorship, something the fediverse aims to avoid. We all shit on meta/twitter/other large corps for censoring content, but when instance owner's do it, its fine? De-federating for ideological reasons like this goes against the principles of federation.
The thing about the Fediverse is that you have the choice to pick an instance. We shit on "big tech" when they do something, because there isn't anything else to do. I personally want to be on an instance that will defed the fuck out of threads (and anyone else who will bring over people who will delight themselves on harassing me and my friends) should they federate, and if you don't want that you're welcome to go to an instance that won't, and we can still talk to each other.
ps: As far as I'm aware, Fediverse never "aimed to avoid censorship" nor had any "principles on federation". In fact, there are large parts of Mastodon (well, mostly Pleroma/Akkoma/Soapbox) filled to the brim with the worst kinda people you can imagine, yet they're all defederated into their own little sandbox. Nobody can decide who can use and build upon ActivityPub but we sure as shit can decide to not federate with a company so shit at moderation that everyone opposing federation with them seems to be a minority in one way or another.