This is cutting off your nose to spite your face.

Most of the activity on any given instance or community comes from outside of the instance. If you start cutting off instances because they are sharing their own stuff with Meta, then you will also be negatively impacting your own communities since the amount of active users will go down.

Most users won't react to something like this by joining your instance or an instance that you approve of (or, at least, currently approve of). They'll either find another community on an instance they're federated with or they'll switch to another social media platform. The latter becomes more likely depending on how many instances end up on either "side" of the issue. Although most user accounts are relatively new, it's still a pain to switch over to something else once you've gotten used to something.

The scale of defederation you propose, especially this early in the fediverse, would be enough to turn off a lot of folks from federation. If admins are just going to defederate from each other at the first sign of disagreement, that weakens my faith in the fediverse.

I absolutely believe that instances should not federate with meta's stuff. The largest servers had enough issues when we were getting new users in the thousands. Meta will likely bring in users in the millions. However, it makes no difference to me if another instance federates with Meta.