Why are so many IT people mean?

Well, I could go into a very long, boring analysis of the type of people attracted to the IT profession, biases you may have based on the sector of IT you work in, the effect of online mediums you may be basing your conclusions on, working conditions and hours, the possibly stressful environment, etc, but that just would be, well, boring.

So here's the deal, it's your fault. Period.

Go out of your way to be exceptionally polite and helpful, you'll find all of a sudden there aren't any "mean" people around.