You shouldn't disrespect someone's wife.
Anthony is upset at Shawn's wife because she has been rude to him lately.
Anthony wants to do something about it.
Anthony tells Shawn's wife that he doesn't want to fight with her, and that he wants to get along.
The next time Shawn's wife slights him, Anthony calls her a slur.
Shawn overhears this and pressures his wife to dial it back.
Shawn gets very upset with Anthony, and their friendship ends over it.