Cambridge does an interesting lob playing a white man turned into a black man, but Van Peebles evidently wanted to make some pejorative assessments of both cultures. The negativity of the film is offset by slapstick and schtik - like the moment of awareness of the transition when Gerber goes to the bathroom in the middle of the night and when he gets off the toilet, a big black rear end fills the screen. The transition, itself, is never adequately explained: recessive gene gone berserk, sardonic God teaching a lesson, who knows?
The sad part of the film is the inability to ever find purchase in the community. Not everyone is bigoted but they are all portrayed as one big cliché. Any normal unbiased people are immediately put off by the reprehensible actions of Cambridge - so there are no friends or allies except of the same race - or more purely - of the same anger.
How nice this movie could have been if Van Peebles had allowed Gerber to rise to the top in spite of everything - to showcase hope instead of futility.