A lot of people dislike it for the privacy nightmare that it is and feel the threat of an EEE attack. This will also probably not be the last time that a big corporation will insert itself in the Fediverse.
However, people also say that it will help get ActivityPub and the Fediverse go more mainstream and say that corporations don’t have that much influence on the Fediverse since people are in control of their own servers.
What a lot of posts have in common is that they want some kind of action to be taken, whether it’d be mass defederating from Threads, or accept them in some way that does not harm the Fediverse as much.
What actions can we take to deal with Threads?
Put another way, given the size of Meta and its userbase, it’s completely infeasible for a typical instance to moderate on their behalf, so defederating due to insufficient moderation makes sense. Just like with Beehaw and sh.itjust.works or whatever. (I take for granted that moderation will suck ass because gestures vaguely at Facebook.)
That’s a good enough reason for me. I also think federating with Meta is a bad idea on principle and out of self-interest, since they will extinguish the fediverse at the first possible opportunity and federating with them gives them the chance to draw in users and later wall them off.