Being a deliberate a-hole with regard to edition war trolling isn't explicitly against the rules, so you get a lot of people who exploit that loophole to be the biggest a-hole that they possibly can be, deliberately.
When no moderator action is taken despite such a poster being reported multiple times, by multiple parties, a well-meaning but misguided poster (or three) inevitably steps in and calls a spade a spade, identifying the troll as such and telling them to bugger off.
The bad news is that calling another poster out like that, no matter how deserved, pretty much *is* against the rules. This results in the person or persons who were baited by the troll being admonished while, often, the troll is left to continue indulging his offensive behavior unabated.
Now, granted, I'm not saying that this happens *all* of the time, but it does happen a *lot* (or did, at any rate). Or it happens enough that I have heard other people frequently cite it as an issue with moderation here.