I've already made my view on the issue known in other comments, but I've just stumbled upon an argument that I think is really important to consider, and should make de-federation an absolute must.

Allowing Meta in goes directly against the idea of Fediverse, and we should fight it as much as possible.

This is a literal quote from the main header on https://www.fediverse.to/

The fediverse is a collection of community-owned, ad-free, decentralised, and privacy-centric social networks.

Each fediverse instance is managed by a human admin. You can find fediverse instances dedicated to art, music, technology, culture, or politics.

Join the growing community and experience the web as it was meant to be.

I've seen a lot of comments mentioning that defederating with Meta goes against the principles and main ideas of the Fediverse, that it should be inclusive and allow people to connect. But, judging by this main selling point of the Fediverse, it sounds to me like Meta shouldn't be in the Fediverse do begin with.