I won't get long-winded about it, but it fits demographically.
When these bastards get worked up about something and concentrate their opinions, they do other, far worse things, like control US politics for the past 40 years.
One can come up with some interesting scenarios if the South was just let go in 1861.
The CSA would have been one hell of a nation, but slavery would have eventually been done away with, and it's possible that left to their own devices, having no one up north to contrast and "threaten" their world view (as they see it), they may well have developed some populist economic policies that would have helped working people somewhat. Seeing everything in terms of opposing what the "yankees" want has given them a reason to tighten up their attitudes on a lot of things that would not be possible if they only had to deal with each other.
On the other hand, the USA could well have developed a successful social democratic political party, elected a social democratic president, and most likely would have been far ahead of where it is today in terms of social welfare programmes.
The CSA would probably have developed a much more radical leftist minority party because of the policies pursued by that government. (Think of Latin America, and the reaction to oppressive regimes.)
Sometimes you just need to let things split, so that each party can do what they need to do. Political marriages are often no different than personal ones. It's perhaps easier now than 150 years ago to make the argument that the US should have just been allowed to go two separate ways.
It's a wild idea, but certainly no more wild than having George W. Bush in power for eight years.
