In his book Conversations with God, James Melvin Washington (whose work predates a book of the same title by Neale Donald Walsch) writes a chapter titled "Slavery and the Eclipse of the African Gods."
Washington's description of Black slaves and their conversion to Christianity suggests this conversion was not the result of "brainwashing" by slave owners in pursuit of submissive slaves. Rather, Washington describes this process as the eclipse of the African gods.
I found his discussion interesting and convincing. If slaves had been "brainwashed" by owners, owners would not have banned private gatherings when slaves met to worship. When you have someone totally under your mental control, you don't worry about what they will do when you're not watching. Additionally, the proscriptions against slaves learning to read would not have been so vigorously enforced if slave owners really believed their own propaganda: slaves weren't very smart and were only fit for manual labor. Do you worry about your dog learning to read if you leave a book in his crate?
"Brainwashed" Black Christians, slave or free, would have been satisfied with segregated balcony seating in churches, rather than advocating for equal treatment and then leaving to create their own congregations when equal treatment was denied in majority white churches.
In his discussion, Washington asserts slaves embraced Christianity as an alternative to their original religions when the African gods--Islamic, ancestral, or animist--failed to deliver the followers from the evils and horrors of chattel slavery in the Americas.
Did these newer Christians make a good exchange?
After all, didn't Christianity teach slaves to obey their masters? Didn't this teaching invalidate any usefulness of this faith tradition for the slaves, those living on the wrong end of this equation?
Consider this: a slave born in the United States in 1800 who lived for 66 years saw (within his or her lifetime) the banning of importation of slaves, the growth of an abolitionist movement, the growth and (expansion into Canada) of the Underground Railroad, a Civil War (1861-1865) over slavery (among other things), the repeal of the Fugitive Slave Law (1864, which required returning escaped slaves to their owners), and finally the passing and ratification of the 13th Amendment to the U.S. Constitution, which banned all slavery in the United States.
All of this happened within a single lifetime. Contrast this to other slavery systems throughout the world, many of which stayed intact for several hundred years. This is why I do not doubt prayers from these slaves were answered.
What, then, can be said about the Bible verses telling slaves to obey their masters? These verses are familiar even to those who don't practice or support Christianity.
Less familiar, however, is the small Book of Philemon in the New Testament. In this book, the Apostle Paul writes to a man named Philemon and describes what Paul will do regarding O., a runaway slave who has come to Paul.
Here is Paul's letter to Philemon: