My history teacher chose one comic from the past to teach on for a whole week. By the end of it, we knew enough and had enough context to get the joke.
Now seeing children reading Garfield, Calvin and Hobbes, and Asterix they often ask: "Why is this funny?"
By explaining, I teach them about the world and the context in which they exist.
Try this question when an adult makes a racist or a sexist joke. Ask them too: "Why is this funny?".
It is a question through which we can explore the history and context in which we exist.