Well keep in mind that of the set of all "toxic" subs, I was only interested in investigating a subset of them. Firstly they would have to be popular. This doesn't actually narrow things down much, contrary to what people might expect.

Secondly, it couldn't be a porn-posting community. Again people tend to think these communities are highly likely to be bad, but a preliminary search showed that that was not actually the case. Perhaps more surprisingly was that the /r/coomers sub, which was the most vocal anti-porn sub, was removed while the porn-allowing subs were generally protected. This probably indicates some site-wide bias or business decision, but I'll leave that up to the reader.

Thirdly it had to be a community that was already suspected of being distrusted. So it's entirely possible that a large sub such as /r/backpacking is actually the worst of them all, but since no one thought to warn anyone else, I simply never looked.

So among the popular (so no /r/kansas), yet distrusted, non-porn subs, it turns out that if I had to "clump" them then it is looking like it will turn out to be the fairly generic cultural bias. I'm sure everyone here probably already suspects, but I'll wait until I can be sure. The reason I'm leaning towards that is because I managed to find a sub that practiced the single worst mod actions I had ever seen: they would bait users into giving normal responses and then secretly ban them in order to waste user's time talking to no one until the user realized there was no more engagement. Every single other subs was brave enough to merely ban a person when their groupthink was challenged. That shows pettiness, but people sort of expect that from reddit. But this mod was so fragile that debate inside of a debate sub was no longer allowed if it appeared the "other side" might win.