I don't think that required a ban, but they are right in saying "we can't see everything" when they say that just showing posts that made it to the top that meet your criteria doesn't mean your post shouldn't have been deleted.
It'd be easy to ruin a subreddit's goals by just overwhelming the mods with rule-breaking content until it's impossible to remove all of it, because then you'd be bound to have at least one example where rules were broken but post is popular.
I mean, I'd argue depending on your audience, "People who meme mental illnesses are just making a clownshow out of mental illnesses" is probably a very popular opinion. like you'd have to go to 4ch probably to get really angry crowds.