I have a ton of respect for Linus Torvalds' technical abilities, and for his way of succinctly and clearly explaining what can often be difficult concepts. However, his off-the-bat lack of civility -- hell, active hostility -- disgusts me sometimes. I'm sure he doesn't care, though: as he said, he's managed to accomplish his goals on the internet just fine how he is. So that's fine, I suppose. I just find it disappointing.
At any rate, there are plenty of examples (no links offhand, but I imagine they're fairly easily googlable if you're curious) of lkmk exchanges where Torvalds is flat out rude to people who are clearly wrong, but, from what I can tell, at least behaving civilly up to the point Torvalds blasts them.
Regardless, though, I still would argue that even in the face of an idiot slinging insults for no reason, "you're an idiot" is a waste of energy and not particularly respect-worthy. Don't feed the trolls.
There's also another attribute of the smartest people I know: they tend to interpret other's responses given the most intelligent interpretation possible.
In the case of some, though, complete neutrality is the best one can do.