Of course just blocking them is an option for the fediverse, but doing that blindly seems like a missed opportunity for both sides.
More freely available content would be great, wouldn’t it?
The issue is once you open these floodgates you're not going to be able to close them, at least not without alienating a vast majority of users on both sides. Furthermore, once meta gains the majority of users and content on its instances (and this is really more of a "when", not "if" situation), they can start making changes to AP and overall infrastructure and forcing other instances to either adapt to that, or get left behind one by one, similar to what google does regardless of W3C and other browsers have to adapt even though it goes against the agreed standard.
If meta gains a foothold in the fediverse and eventually start isolating the smaller instances, it's going to be the email situation all over again, we'll have just a few large trusted providers and the rest will be a seemingly unsafe niche that most people avoid. Giving them the benefit of the doubt is just foolish, meta will not let a few fediverse admins dictate their policy (even assuming they have the backbone to stand up to them, and considering the recent meeting/NDA/"shareholder" drama most of them definitely don't).