The three most intelligent black guys I knew all spoke perfect English, other than the one that liked to josh us now and then by pretending to go ghetto..
“Black Acting School” from “Hollywood Shuffle” (Language)
https://www.youtube.com/watch?v=_ASZ6K9cPNk
A college classmate, whom I have also worked with as an engineer, is originally from Nigeria and tends to look at the “urban ghetto jive culture” with disgust. When encountering such “jive”, he responds in perfect British Empire English with only a hint of native accent.