If someone has started a debate, then it's OK to argue on the topic in question. But I've seen examples here and elsewhere, where contributors have been called stupid (among other things) for holding the views they do. Then people agree just because they happen to be friendly with the person who said it, not necessarily because it's a view they hold. And that's not OK. People should stick to the question and not get personal, because when they do, it shows them up for the ignoramus they really are.
There's a particular saxophone forum I visit which is moderated (solely) by some dictatorial bully of a bloke who deletes anything he doesn't agree with (or posted by anyone he doesn't like) - and that's a lot. The worrying thing is that many of the contributors are impressionable, gullible even, teenage music students who hang on his every word and blindly follow him in ganging up on anyone who dares to suggest that, perhaps, he mightn't be the big 'I am' that he thinks he is.
I've seen this same person's name around other sites, spouting just the same rubbish he spouts on 'his' forum (it's not actually his - he just co-erced the owner into sacking the last mod and letting him do it). Fortunately most sax players are of a reasonably grounded breed and either ignore him or give him as good as he sends, but I really think he only frequents internet forums in order to get his little power trip. If he really is a teacher, as he says he is, I suspect he's not a very effective one because his students would be terrified of him.
Unfortunately that site is by no means the only one I've come across, but on the majority of sites I stick around moderating is done by a team who also act as moderators to each other and who are known and may be approached directly.