I can see why many Southerners, black ones in particular, don't like the implication that Southernness and the Confederate heritage are one and the same, because they're not. On the other hand, there are people who want to extirpate that completely and want folks to spit on the graves of their ancestors.
You ask people what their ethnicity is, and a lot of Scots-Irish people either don't know or if they know it they just don't acknowledge it. It's not something they really identify with. They're just plain old Americans, plain vanilla. I don't think they are a self-conscious voting bloc.
I think there's a suspicion in the South of people putting on airs. You see it in most successful Southern politicians, but you also see it in someone like Richard Petty, who may be a multimillionaire stock car driver, but he's also beloved because he has a nice self-deprecatory way about him.