And the answer is: racial prejudice. If you don’t know the plot of this musical and think it’s just something lighthearted, you might be surprised by its content. The location is an island in the (where else?) south Pacific during World War II. The central conflict between the two main characters, Nellie the Naval nurse and Emile, the French planter with whom she falls in love, is that Nellie finds it very difficult to accept that Emile has been married before to a “dark-skinned Polynesian” and has two “mixed race” children. It’s only after Emile is almost killed in a secret mission to spy on the Japanese forces that Nellie realizes how much she loves him and his children. Another character, the Naval officer Cable, falls in love with a Polynesian girl, Liat, and that romance is also considered pretty scandalous. He decides that he can’t marry her because of how his family back home would react. He’s killed during the spy mission. But before he goes off to that fate he sings a very famous (and controversial at the time) song about how prejudice develops: “You’ve Got to be Carefully Taught.”