I didn't see this when it was broadcast, and I'm not sure I remember this specific episode when it was in reruns, but I've been aware of the episode for a long time.
The plot of the episode involves Lamont's attempt to rehearse the role of Othello with Marilyn, the woman in charge of his drama workshop. I wish I could give you the entire episode because there really is a lot of thoughtful material in what seems like a silly seventies sit-com on the surface. The episode thinks about black and white reactions to the idea of a black man murdering a white woman.
I've put together a clip with all I can give you, and it breaks into four basic segments: The Shakespearean Setup, Fred's reaction to his son's rehearsal of Desdemona's death scene, some riffing on Shakespeare, and Marilyn's parents' reaction when they see the same scene.
Throughout the show, there's an uneasy conversation about bigotry, about how white people are viewed in the Watts area of Los Angeles (then primarily black) and how black people are viewed in Beverley Hills (then predominantly white), and about underlying racism.
After Fred Sanford breaks up the rehearsal at the Sandfords' home, he asks why they can't rehearse at Marilyn's house. When he learns that she lives with her parents in Beverly Hills, he declares that to be the reason they can't rehearse there. But, to prove a point about black people being welcome in their home, Marilyn insists that they move the rehearsal.
Marilyn thinks that her parents are out of town, but they've actually gone to bed. Fred Sanford, bored by the rehearsal and searching for the TV, accidentally walks into their bedroom. When he tells them he's just looking for the TV, they fearfully tell him that he can take it.
After everything is explained, Fred accuses of the parents of being bigots because they assumed that he was there to rob them. The mother says that they're not bigots, offering this proof: "We both belong to the Urban League." The father keeps referring to Fred as "a strange man," at which he takes great offense; Fred refers to the family as "you people," which the father takes as an indication of intolerance on Fred's part.
The show thus asks for a deeper consideration of actual, potential, or latent racism, using Othello as a starting point for doing so.
Here's a clip that has most of the Shakespearean elements of the episode:
Links: The Episode at IMDB.