If there is a threat to all the users of #Mastodon that would be posed by #Meta merely being in the #Fediverse, then what is protecting those users from the numerous unknown instances that are already here from doing whatever it is Meta is going to do?
The campaign to preemptively block #Threads seems to me to imply there is some fundamental architectural flaw in the #ActivityPub protocol that admins are currently relying on security by obscurity to mitigate. If so, then the actual problem is Mastodon itself, and federation should be abandoned entirely until this flaw can be corrected, rather than using band-aids like blocking one big instance and then relying on the goodwill of individual admins to keep the system safe.