if I wanted to bring the Fediverse down or at least keep my customers from going there, I would sow this stuff as much as I can
Agree. And that's been my experience here too. I made two posts critical of reddit and they each seemed to have been astroturfed by toxic reddit shills.
I think it would require a lot of active and dedicated mods and admins, which I'm doubtful is doable. I don't know that there's a fix for this but a "true block" (instead of the current "mute") might help; but there are major downsides to that type of feature as well. I wrote in a blog that it might require an advanced AI to moderate everything.