An almost humorous footnote to the benefits of having a Christian slave master is in Narrative of the Life of Frederick Douglass.
Young slave then, Douglass was with a cruel master, Hugh Auld. So irreverent before his conversion at a Methodist camp revival, Master Auld would wait until the Sabbath for to beat "bad" slaves.
Douglass witnessed Auld's conversion and wondered what effect it would have on the man.
After the Lord "saved" him, Hugh Auld beat his slaves on Monday.
I read a slave account that noted that slaves sold to Louisiana plantations were grieved to find that those predominantly Catholic planters tended to work slaves 7 days a week as opposed having to work only 6 days for those of the Protestant denominations.
Religious slaveholders were delicate not to separate and desecrate marriages between slaves by having to sell a husband or wife-
--Solution? Do not allow a "legal" or "church" wedding! Hence the slave custom of "jumping over the broom" to symbolize a union. There was, as a result, immediately following the Civil War a tremendous surge of legitimizing the unions of couples so long denied the dignity of recognition.
There is no end to the hypocrisy needed to buy and force labor from another human being. And Christians proved well able--justified often by their church leaders--many of whom held slaves themselves.