I'm split on this myself.

On the one hand, I do think there is a risk of Meta's influence becoming too pervasive over ActivityPub and ultimately kneecapping it. I think to presume this couldn't happen is naive. Further, Meta does have a history of trying to bring everything under its own umbrella, and if they see enough profit opportunity in trying to own the protocol then they will sink serious effort into doing so. They have done it with many other companies & ideas already.

On the other hand, preemptive blocking is not in the spirit of the fediverse, users should be able to make their own choice, and SDF is known for its general openness. "Why in this case and not others?" is a real question.

I personally don't think the influx of users/content & problems with "Eternal September" are too big a deal. True, I'm not a sysadmin or mod here. If those were real reasons to block the service then we should do it on logistical grounds without hesitation - there's no need for user input or discussion in that case.