Pointing someone out as a rube is hardly a Northern to Southern thing, and I don't think there's any way you can prove it's some kind of isolated attack. How many times have we all seen jokes about Canadians in that vein, especially the ways their speech differs? Or someone from Idaho. Or people from Maine and the whole "ya can't get heyah from they-yah" thing? Or the millions of souls in places people deem "ghettos"--which may occasionally get some cool points in this rap-age, but also bear other more negative natural assumptions.
Bucky doesn't seem like a dumb guy at all. But Kellie does. It doesn't have much to do with where she's from--she just is.
Bucky might be a bit style challenged, but that's hardly the sweeping and unfair indictment that assuming he's dumb is.
He's also a bit trapped in certain elements of his local culture which don't always translate that well to the whole nation. Again... not dumb. But it's a valid criticism if you are trying to build a nationwide star. Carrie Underwood was a bit of a country mouse too, but something about her obviously transcended her origin. Certainly it could happen again.