Why are so many teenage black girls like this?

First, I believe everyone can be that way. Maybe the black teenage girls you are talking about had a bad day or someone was getting on their nerves. I am not gonna lie, I can act that way at times, but I am not gonna let anyone talk to me or treat me any kind of way. That is not the only side black girls have, we can be very affectionate, caring, loving, laid back, and fun to be around. It all depends on the person. You can't catergorize all black teenage girls like that. Personally I can be both.