We've been moving along with false history since the 1860s, no doubt due to the fact that most of the publishing companies were in the North, and also because it was in the best interest of the majority to justify what they had done to the minority.
No, all you have to do is read their own words. Its hard for us to put ourselves into their mindset, because that mindset doesn’t exist anymore here, but they actually believed their system to be a righteous one worthy of defending and worthy of propagating. They say so quite clearly and quite proudly.
This does not mean every southerner was evil or every northerner was righteous. The truth is actually more interesting, as good men fought on both sides. When you see that many of the generals in the south along with their soldiers were devout Christians, that only makes the whole thing that much more interesting.