Blond (and other "hair type" stereotype) jokes are only funny because the stereotype is that blonds and dumb. But I don't get the point of them because there are plenty of other things, such as just saying "idiot", which does not have to be a blond. So you could just have idiot jokes, and not be mean with people who are blond and aren't stupid. Then again, saying, "There's an idiot, a person who's really talkative, and this person who blank blank blank", is longer and harder to remember than "Theres this brunette and a blond a a redhead..."

I still don't think it's nice, but it can be funny in SOME cases.