They never have to. That's a big problem. Kids are not taught that democrats were running the south. They aren't taught that KKK was a product of the democrats.
However, I think that most reasonable people do not associate the attack on Ft. Sumter as a war of northern aggression. I guess the democrats will call the blitzkrieg a war of Polish aggression. Defenders of the democrats are quick to say that the war had nothing to do with slavery. Democrats say it was about states' rights...........to have slavery.
But, the democrats have every right to defend slavery and the confederacy, just as they have the right to look like fools. The democrats can refer to Lincoln as the great butcher all they want. But they will never be able to say the democrats changed the constitution to ban slavery. They will never be able to say that they fought against slavery. Just as they wanted the black man to be dependent upon somebody to live and function back then, they want the same thing now.
How do you explain slavery in the Union states?