The republican party was formed to fight slavery. The democrats, both north and south fought one way or another against the republicans. You're talking about the "proud heritage" of the democrats, NOT the republicans.
But the southern democrats changed parties. They are all now republicans. I guess you just don't get it. The solid republican South is made up of Christian men and women who are not going to give up on their heritage just to please the country club republicans from the North. We sing, "Dixie", love rebel the flag, hate abortion, are disgusted by the gay movement, etc. We are the heart of the American Republican Party. Just ask our Southern president. Yes, Texas was a Confederate state.
Concurring bump. 'Bloody' Kansas is a much more solid red state than any of the former Confederate ones.