[As an aside does anyone moderate this place? It seems to me that there are similar threads on some subjects but they never get linked together]
That's a very rare occurance, mind. In my eight or nine years here I can only remember three. People do tend to play nice. Obviously, as we're disembodied it's easier to be rude, and on U-Know we're discussing things that we're passionate about on a deep moral level, so it does get heated now and again.
But if someone starts getting personal, pointing out to them that they're not going to win the argument that way, that if they're smart and right then fact and reason should do the job, and appealing to their better nature almost always works.
Not only does that not lead to the sour taste of bannings and suchlike, but it means we don't lose people who have a lot of valuable contribution to make.