At times humor is like music, something that you find of your liking or fun at some point, becomes absurd and despicable at another. If your impressions on this young man are right, he is still a good person worth your consideration. For some reason he found the joke fun, he shared it with a good intention and most likely he didn’t consider all the implications. As I see it, just asking him why he thought the joke was funny might clear up things.