*****BLONDES ARE NOT DUMB*****
Dumb blonde jokes are perpetuated because people write such characters into TV and movies and blondes are willing to portray themselves in such manner. If they weren't, it might take a while, but the stereotype would die, because there are stupid, vacuous people with all hair colors and races, but the blondes are the ones falling all over themselves to go to the casting calls to be portrayed that way. What it comes down to is, it's up to blondes themselves to eventually negate the stereotype.