Education.
Sometimes I think we're alone. Sometimes I think we're not. In either case, the thought is staggering. ~ R. Buckminster Fuller
To be fair, the South's entire economy was basically built around slavery. The economic depression resulting from its removal, as well as the damage of the Civil War, was something that the Southeastern United States only really began to claw its way above in the later half of the Twentieth Century. Given that fact, it's not hard to see why many Southerners were wary of having some Yankee president all but "pull the rug out" from under them while sitting pretty in a part of the country that would be more or less completely unaffected.
It's also worth noting that there were a number of people in the South who actually wanted to move away from Slavery anyway. They just wanted to do so more slowly, on their own terms.
No political ideology helped cause the tragic murders in any way, shape, fashion, or form. Whoever murdered the nine innocent humans caused the murder.
Whoever did this was likely an extremist that acted alone and was off the deep end in the first place...
It is evil to even suggest such a thing. The response from the people involved is the most incredible thing I have ever seen. I wanted to go and meet those people but I live too far away. I know many people who CLAIM to be Christians and go to church several times a week but most of them are hypocrites. I believe those people in Charleston are the real thing.