Slavery is, obviously, supported in the Bible. Slavery was defended in the Old South by good white Christians who relied on the Bible to justify their immoral, unjust, and oppressive culture. What many don't realize, though, is how extensively intertwined Christianity and slavery were in the Old South. In many ways, the Civil War as a much a defense of Christianity as it was a defense of slavery: the elimination of slavery meant the elimination of an institution grounded in Christian doctrine.
In Rebuilding Zion, The Religious Reconstruction of the South, 1863-1877, Daniel W. Stowell writes:
Methodist Ell Gertrude Clanton Thomas, a member of the planter elite in Augusta, Georgia, owned more than ninety slaves; the Civl War destroyed much of her wealth, and she and her husband were “reduced from a state of affluence to comparative poverty.”
Until emancipation, she had not realized “how intimately my faith in revelations and my faith in the institution of slavery had been woven together ... if the Bible was right then slavery must be — Slavery was done away with and my faith in God’s Holy Book was terribly shaken. For a time, I doubted God.” ...
Reluctantly she admitted, “Our cause was lost. Good men had had faith to be lost? I was bewildered — I felt all this and could not see God’s hand.”
Christians seem to have a remarkable ability to attribute to God and God’s will just about any attitude or belief they themselves hold. Whatever they want, God also happens to want. Whatever they believe, God also happens to believe. When Southerners wanted slavery, they managed to find that God also supported slavery. When Southerners wanted to leave the Union and create a slave-holding nation, they managed to find ample support in God’s words for that as well.
Were they just making things up? Of course not — at least, no more so than Christians today or at any other point in history. The simple fact is that just about any position, idea, or practice can be supported by scripture and tradition if you put a little work into it. This is hardly a surprise given just how diverse the authors of both were. Scripture was created and edited by very different people over the course of centuries; tradition was created by innumerable people in different cultures over the course of millennial. There's a tremendous amount of material to work with, so it would actually be surprising if Christians couldn't find just about anything they wanted.
It's common for Christians today to argue that their religion and their holy scriptures should be perceived as forces for good in the world, but a more sober evaluation must take into account not merely what Christians claim about their beliefs, but also how their beliefs have been used by Christians in the past. When it comes to slavery and the Civil War, we have one of the clearest examples possible that Christianity can become part of social institutions which oppress and kill.
Today there are many conservative Christians who believe that if the Bible is right then evolution must be wrong, or that if the Bible is right then homosexuality and gay marriage must be wrong. Just how different are such attitudes from the attitudes of Christians in the past like Ell Gertrude Clanton Thomas who believed that that if the same Bible were right, then slavery or segregation had to be right? I can't regard anti-emancipation Christians like Ms. Thomas as any less sincere, serious, or devout than anti-evolution and anti-gay Christians today.