The Spook Who Sat by the Door (1973)
Dan Freeman (played by Lawrence Cook) is a token black CIA operative. Trained in all sorts of espionage, he is relegated to working in the copying department as a "showcase" employee of integration. As the title suggests, he's placed by the door of the office so he's the first person everyone sees. Incensed by his mistreatment (and the racial stereotyping of his superiors), he resigns to his native Chicago as a social services worker.
Secretly, he is training a street gang into a guerrilla army to be the vanguard in a race war, using all of his training by "the man" against "the man".
The details are impressive. Freeman explains how to establish a hierarchy in an underground movement, how to recruit new members, living on the street, and forming new cells. He also details how racial stereotypes can be used to one's advantage, citing how no one ever notices a smiling black man in an office carrying a mop.
The film is a faithful adaptation of Sam Greenlee's controversial novel of the same title, and a haunting look at what MIGHT have (and maybe damned near) happened in the USA during that turbulent period of history.(IMDB Baroque)