From The Onion's interview with Melvin and Mario Van Peebles:

O: Were there any cinematic images of blacks before Sweetback that you connected with, that you thought had the ring of truth?

Melvin: One. That was Dooley Wilson in Casablanca. He didn't have to shuffle or do nothing. He just played the piano. In the ghetto, we'd make them stop the movie and re-run it, put it back in, because we'd never seen that.

As for Baadasssss! itself, it's fun, but a little sloppy, and its use of first-person narration is ill-advised, since it often forces the main character to provide a self-congratulatory commentary on his own actions. (There were moments that reminded me, unfortunately, of Big Fish.) I think it's an important rule of screenwriting that first-person narration should only be used by the lonely, inept, neurotic, or chronically depressed. (It isn't a bad rule for blogs, either.)