Though there is truth to the Bill Cosby thing, this is only one side of the blame. Your argument is the other side of the problem. It is collectivist in its roots, viewing blacks as a "community" rather than as individuals.
Your claim seems to be that blacks as a whole do not deserve respect so long as ghetto culture exists in a large part of their population.
Is this to say that Bill Cosby, Colon Powell, and Condaleeza Rice all deserve to be frowned upon for the actions of a large group who share their color... or that they should be seen as "a credit to their race" because of their color? No. They should be seen as individuals, as should the rappers who are their antithesis.
The white kids who copy "black" fashion and slang are to be judged as individuals also. There is no justification for broad-ended assaults on a race over the actions of some, even of many. The concept of racial difference is something that should be destroyed, not perpetuated by ideas of collective guilt for a race.

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"Man lives in the sunlit world of that which he believes to be reality. But unseen by most is an underworld, a place that is just as real... but not as brightly lit... A DARK SIDE!"
-opening from Tales From the Darkside