> We would line in a very different country if, after the civil war, every slave owner was strung up from a tree and their estates were redistributed to the formerly enclaved.

Yeah, but not for the reasons you think. A country that would just kill a significant share of its citizens for something that used to be legal very recently is not going to end up just fine. Moreover, due to normal distribution of human traits the next generation would have the same percentage of 'evil' with or without your well-intentioned genocide.. go figure.

> the dark side of slavery

oh mate