Religion and Slavery

I think it's sort of ironic that the narratives we have read so far both strongly emphasize the importance of religion in the lives of slaves.  Christianity argues that all men are equal under god, and that slavery is wrong.  Yet many slave owners were the ones who pushed religion on the Africans, and saw them as lesser people because they were not Christians too.  I don't understand how these people could claim to believe so strongly in Christianity, yet choose to ignore one of the most fundamental aspects of it.  And why did the slaves, who were not treated equally even as Christians, still choose to follow this religion so strictly?