Evidence to that can be found all around the world, specially some years ago when slavery wasn't aborted in many countries. Hypocrisy in this case, would be from the people that slaved to the slaves, since they don't agree religiously, because they have different religions and beliefs.
And that is why, in early times, people that where religious and contributed a lot (with money) could have slaves and do all sorts of things wihtout being accused by anything.
Hope it helped,
BioTeacher101