I don't really perceive myself as being Not Nice; people who are deliberately Not Nice generally strike me as self-involved dorks with low self-esteem whose one bright spot in a dull existence is that they have within their power the ability to make others as miserable as themselves. Obviously, I don't think that's true about me. I just don't suffer fools easily.
Upon further thought, I find it a bit odd that "Nice" should be held up as an ideal of conduct, as something one should aspire to be. Nice doesn't really work very well. It's not that it's ineffective personally; nice guys may finish last, but that's irrelevant to the point I'm trying to make here. It's that it's ineffective societally. Nice doesn't get anything done for anyone. Nice people say "there there, dear," but they don't give you the last quarter you need for your laundry. They say "why there ought to be a law," but they don't stand on street corners in the wind and rain trying to get signatures on the initiative. In short, Nice is a weak excuse of the lazy and incompetent to avoid making any effort.
I'm a sweet person, a compassionate person, an interesting person, a passionate person. I try to save worms on the sidewalk; I give flowers to my partner; I let my friend stay at my house for free, for months, so that she could get a job. I try to act in a positive way on the universe at large. I succeed at least some of the time. However, I'm occasionally crass, crude, short, terse, bitchy, or downright mean. In fact, I'm Not Very Nice.
You got a problem with that? Bring it on, poptart.