There's a movie from 1978 called "Blue Collar" that makes a powerful statement about the different ways the working class is set against itself. It has Richard Pryor and Harvey Keitel in it and people typically think of it as a comedy but really it is not. It explores some really dark themes about American working class culture.
Edit: I found the tralier on youtube.
Then the "You're thinking white" scene. (Warning, there's profanity in this scene, if that offends you don't listen.)
The ending says: "They pit the lifers against the new boys, the young against the old, the black? against the white, everybody, to keep us in our place!"
It had a powerful impact on me the first time I saw it years ago.