I don't agree that defederating with Meta is against the definition of Fediverse.

This is the header on 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.

Meta-owned instances go directly against every one of those points. For me, Fediverse should always be run by people not doing it for monetary gains. The main advantage of fediverse is not that you can and should connect with anyone, but that it's a community that is not ran for profit, and the servers are run for the people with good and self-less intentions, instead of users being heavily monetized and their behavior fed into algorithms to manipulate them even further with the content they are shown. And the federation is there mostly to alleviate a problem that usually happens in such comunities - people move on, servers die, admins can't run an instance any more. With fediverse, this is not that big of an issue, thanks to the way it's designed.

Allowing Meta, or any large company in that regard, in will destroy this idea of community run and privacy-centric social network for everyone, and only result in Meta profiting from it and the content the users create.