Not to discourage new answers, but this has been discussed before /u/ThanklessAmputation has a reply to it here about it.

Also a related question on Is there evidence that the FBI flooded black communities with drugs in the civil rights era? answered by /u/A_Soporific here

Also a comment by /u/mooselover801 on Is there any truth to the claim that the CIA peddled drugs to black communities in the 70s and 80s?