I'm pretty sure that U.S. soldiers shooting down camp guards is a given. They already show indifference toward Confederate civilians committing suicide after being shown the mass graves.
I doubt that Morrell, where he's at by Atlanta, will run into the camps. The death camps were located in Mississippi, Louisiana and Texas -- far to the west. In fact, they're in locations that would be the last to be touched by U.S. soldiers by where they're presently at, so the Snake could take joy in the notion that as he's preparing to go down blazing, his revenge on the blacks will go on to the final moments of the war.
"No, I mean socially. The Confederates will hate the USA even more."
Maybe. Maybe instead -- after a hefty dosage of Reconstruction, of course -- they'll learn to accept the USA for what it is, and realize that its a hell of a lot better than the idea of the "decent white folks" country that their mad president had desired.