If you keep playing with fire, you inevitably burn yourself.
Also, while I know you're not the kind of person who responds well to being told what he can or cannot do, let me be perfectly clear. Until you appear on the list of administrators in this community, you don't get to decide what is or is not "quality mod behavior". We can sit around for days - if not weeks - deciding whether or not getting the last word in is mature and get into an unending circle of closed topics and response threads, but the fact of the matter is that Deman has earned the level of say-so he has in the community.
That isn't to say that I condone every detail of his closing post (his choice of language was, obviously, not what I'd call the gold standard), but I understand precisely what caused it, and comparing his actions (and, indeed, the actions of most of the forum staff) to an inhumanly cruel and maniacal regime is just asking for trouble. If you didn't want him to react that way, you shouldn't have pushed him.
At the risk of drawing further, "enlightened" comparisons from you, I'm closing this topic and am going to remind you that, since you're not issuing a warning, you are expected to carry this kind of post out in a private discussion.