I hesitate to speak for the Divine.
I would suggest that being opposed to Slavery would put one on the side of the Angles, while being a supporter of slavery would put one into the opposition.
And yet you still deign to do so. How many times did God send his own people into captivity? Captives not killed were what?
One hell of a War, as all wars, are. Human dignity, always seems to be the challenge, amongst humans. Story of Life.