Sermons were preached defending slavery as being quite biblical. It was felt that personal prosperity would be threatened if the system were stopped. For a hundred years or so only a few nuisances or religious nuts campaigned to stop slavery.You should bear in mind that the prosperity of the British Empire depended critically on the use of slaves. This is why Britian under Queen Victoria was careful not to interfere, or take sides in the American civil war.
I intend to deal with the biblical theory concerning the sin of Ham elsewhere.