Saying that all rap music is the same mindless dribble means that you are completely unaware of the "whole" of rap music, and generally, you don't care to know.
The problem with popular rap, is that rappers are paid to sound like bigots, women abusers, coke dealers, cop killers, when none of it is actually true, THEN is marketed towards kids. See.. this is how capitalism destroys art. When your goal isn't to make money (or popularity for the sake of money), then your artistic expression would have been self-driven, an actual sacrifice of human time, in which you would use it the most wisely. If your goal is making money, then you will make the least-personal, most relatable and marketable thing you can for the sake of accumulation. It's not black and white, there is gray area in between.
There are more rappers who rap about poverty, war, politics then there are who rap about pimping, guns, what have you... they just are paid and advertised.
However cool is defined in culture will be the reality for anyone who falls under it's hypnotic spell.