Just because someone says something is one way, doesn't mean everything else is the opposite. I think perhaps one of the reasons people think south = super polite is simply because etiquette and words like "sir" or "ma'am" are drilled into children from an early age. In the North, where I grew up, people take a more subdued, common sense approach. In my opinions, it seems to average out so people from both areas are roughly equally polite, it's just some people are more formal about it.
