In Brazil and Haiti (and also in the other French colonies during the monarchy), the goal was to work the slaves to death. This was also done in the US, but when the Brits started capturing slave ships and the plantation owners considered that slaves could be a more valuable cash crop with no competition from abroad, the US decided to ban new importations, at least legally. Plus, the Plantation owners liked to say that the Plantations were much better for the darkies than the jungles of barbarous Africa, plus, the slaves got their souls saved as well, an added plus, with Biblical justification.The slave population increased in the South even more than it did no Brazil, where new slaves were imported all the time and legally.
Jefferson Davis' brother had a plantation on some legendary isle in the Mississippi where the massa rarely bothered to visit, and where everyone was a darkie, happily toiling away and singing and dancing and jumpin de broom jes' like in Uncle Remus.
This is the myth of slavery that Plane is quoting. Southerners believed that slavery wasn't all bad. It was, in many ways, a GOOD thing, and economics was on the side of decent treatment, because the market is always wise. The Northerners, they just didn't understand.
It is harder to kill a myth about barbarism than it is barbarism itself.
The rightwing always wants to return to them good ol' days, when justice always came swiftly with a silver bullet and left with a hearty "Hi-yo Silver, awaaaaay!".