You mean that you have different starting assumptions when acting as a scientist than you do when acting as a Christian. Compartmentalization. I see you ignore the uncomfortable questions about bad things happening to other people.
I don’t think it’s nebulous at all.
Not mutually consistent, though. And the point is that the doctrine of God’s image, of itself, has no implications for human equality. Depending on auxiliary doctrines, you can come to any conclusion at all.
I don’t think the historical development is all that Christian either. Certainly Western civilization passed through a period in which morality was infuenced by Christianity, but then again Christianity was influenced by a host of other traditions. There’s nothing all that new in it.
We’ve established that there is no such thing as “the conclusions of Christian morality”; rather, there are a great many sorts of Christian morality with different conclusions, and thus different Christians were able to support both slavery and abolitionism.
Nobody is doing such a thing, so arguing against it is pointless.