The quote is:
For this reason, the atheist who cannot believe for moral reasons does honour, in an elliptical way, to the Christian God, and so must not be ignored. He demands of us not the surrender of our beliefs but a meticulous recollection on our part of what those beliefs are, and a definition of divine love that has at least the moral rigour of principled unbelief. This, it turns out, is no simple thing. For sometimes atheism seems to retain elements of ‘Christianity’ within itself that Christians have all too frequently forgotten.
And the writer is David Bentley Hart, American Eastern Orthodox Theologian, from his book The Doors of the Sea, about suffering and faith. p.25.
I hope to post a review of this interesting book soon.