That's a very complex question, as you know. I suggest picking up a copy of "American Slavery: 1619-1877" by Peter Kolchin, which is a good overview of the various types of slavery in various periods. There is plenty about the master-slave relationship. The ideology that was in effect in the large Southern plantations during the 19th century was paternalism, which was a faux family relationship. Masters were "protecting" slaves, who where seen to have minds like children, from the outside world. As long as masters kept slaves alive, it was seen as a kindness, compared with the "brutal" world of Africa or free capitalist society. The truth is that master-slave relations ran the gambit, so this is a difficult subject. You may also want to read Booker T. Washington's "Up From Slavery" for a first hand account of this relationship.