I see that as 2 conflicting statements Fred, is it natural or is it taught?
Personally I don't know, it's a chicken-egg situation, I don't know how anyone could claim to know. I can see why people feel it's natural to dislike baldness, it is after all unattractive, shows aging which people don't like (reminder of death), I can also see why because of the amount of abuse bald guys get in shows like this one and other cartoons and films, people think that we're being taught to hate bald people.
But why? It's just an easy and "acceptable" target to hate on bald guys, nobody will get any backlash for it, most people agree that baldness isn't good, and a lot of people are insensitive and can laugh at baldness. If anyone thinks there's a bald conspiracy, then that's crazy to me.