Instapundit, being a more reasoned and reasonable person than I, chalks it up to ignorance:
IS “TEABAGGER” THE NEW “N-WORD?” No, but when I hear someone use it, I know that nothing they say on the subject is worth taking seriously. Either they’re deliberately using it as a sexual slur, or they’re too ignorant to be worth listening to.
My reaction to hearing someone use the word "teabagger" is hypocrite.
As long as I can remember, liberals have claimed moral superiority over conservatives based on their "open-mindedness" and "tolerance". As a result of their vast intellectual curiosity and acceptance of varied points of view, they thought it only "right" that they belittle stodgy, dull conservatives for being "judgemental."
If we've learned anything from recent events, it is that liberals are close-minded, intolerant, whiny hypocrites. And yes, they're ignorant.