And some of the most vehement supporters of slavery were also church-going Christians and their Pastors/Priests.
Traditionally it had been argued, and still is argued by some fringe sects, that the "Curse of Ham" from Genesis 9:25-27* justified the enslavement of Africans (saying that Canaan had settled in Africa and that the darker skin pigment was the mark of the curse).
*
Genesis 9:25-27 (New International Version)
25 he said,
"Cursed be Canaan!
The lowest of slaves
will he be to his brothers."
26 He also said,
"Blessed be the LORD, the God of Shem!
May Canaan be the slave of Shem.
27 May God extend the territory of Japheth;
may Japheth live in the tents of Shem,
and may Canaan be his slave."