Summary:
I downvoted pro-AI comments in a post in leftymemes community. It was LLM generated polandball comic (Which is objectively pathetic as fuck) that showed up on my feed, blocked couple of users who I thought were unhinged, and have blocked the whole instance on my client after realizing how rabid these morons are.
I didn't go looking for AI posts like a vigilante.
One user in question got miffed for being downvoted and banned me from places they moderate.
When you have dozens of that one person the effect is the same. Downvoting something you don't like in an instance dedicated to that something derails the conversation and inserts unnecessary negativity ala downvote bots; at this point block the community and move on. Imagine if Lemmy had dozens of religious people downvoting the shit out of all posts on c/atheism or c/atheistmemes.
My dude. That's voting. If everyone organically decides to not like a post, they can downvote.
Briggading is the very specific case of organizing a bunch of users from one forum together to downvote something on another.
If you don't like AI posts, then you shouldn't be on pro-AI communities. That'd be like an atheist downvoting everything on c/christianity (which is probably not a thing) or vice versa, a religious person downvoting everything on c/atheism. If you fundamentally disagree with what a space stands for, then your vote is indistinguishable from brigading.
That's the promblem. Your analogy is flawed because OP and others like them (I copped a ban for my participation in that thread) had no reasonable way of knowing in advance that c/leftymemes is a pro-AI community. It didn't say anything about it in the community rules at the time, and it's only when people reacted negatively to someone posting an AI image and the mods cracked down that we found out.
I don't, and I assume OP also does not, go around commenting in comms for genAI content. If I see one in my feed, I just block it. It just wasn't really knowable that c/leftymemes is a genAI comm.
Lefty memes isn't pro AI (though they're not exactly anti-AI either); I saw the bans and thought they were downvoting stuff on the communities in the mod log. Also OP was in flippanarchy (which also isn't explicitly pro, though also not anti, AI), not lefty memes. It seems the mod banned OP from their comms on their pejorative, at least with the information we have. I edited the parent comment to that effect.