You can defederate from their server, but if they “embrace, extend, extinguish” the ActivityPub specification, then the game is over just as well.
I don’t think that’s the case here. Enough of the fediverse is resistant to Meta’s play here to keep a significant chunk of ActivityPub platforms running on spec and able to interact even with a Meta-fied version of ActivityPub existing. Other examples of EEE happening to open source standards seem to start with the community generally trusting the big corps to respect the standard where here no one expects Meta to play nice. The fediverse is an internet within the internet and Meta’s biggest bargaining chip to join up is a large user base but if the fediverse is fine staying small (which I think it is) then there’s no need to play Meta’s game.
