> I don't think we can credit it with a value system that has sympathy for the fundamental humanity of the enslaved.

We can because there is a difference between introducing a new moral grammar into the world and what people do with it. The claim is not that Christians as people were any more moral or less power hungry than people tend to be, it's that from that point on in world history, they had to be hypocrites, precisely because something had metaphysically changed.

The Enlightenment doesn't stand in contradiction to this, it's the culmination of it, which was most visible in particular among the American abolitionists. Who more than anyone else staked their claims on Christian (and Enlightenment) grounds.

And as a practical point when it comes to today's issues. Pay attention to what the post-Christian secular America looks like. Because unlike the British humanists who thought equality was just common sense, you're going to be in for a wild ride, which Nietzsche did tell us.