Cultural differences - at times it amazes me how uptight anglos can be with a little sexual humor...
Man, in the hispanic community parents tell jokes like that to their kids, and vice versa. Everybody laughes and nobody's uptight nor offended. Sexuality is a natural and wonderful part of life and it's perfectly fine to talk about it, joke about it, without some big, oppressive Victorian-age tabou forcing veryone to act and talk like repressed puritans. But it doesn't mean that kids will grow up to become sex-crazed freaks. Quite the opposite, they seem to have a more mature and understanding attitude.