Slavery is worse than murder? I don't know about that. Never mind many of those regimes that were murderous also had slaves in the millions.
It's not great, but frankly the fact that not everyone had to go around fearing for their very lives is telling.
I did not say that the Confederacy was more brutal then the regimes you cited.
What I said was that it was the worst kind of tyranny, that is, a tyranny that shrouded itself in the cloak of morality.