This is a remarkable concession! Oh, but if only he had stopped at this paragraph. If you take it seriously, then you should be the one on the defensive. Why spend your time trying to fight the consensus view of modern biological science? Why fear that accepting the truth of evolution will throw society into a nihilistic abyss, as, say, Phillip Johnson does?
Once you accept this paragraph's argument (as I, an Objectivist, have argued here for some time now), then the real debate is: Can what you call "spirituality" be created by a natural process, or is some kind of "supernatural" designer required? I think there's no reason to believe a supernatural person is required, and apparently you do. But we both agree that humans have a "spiritual" capacity! (I'd say humans have rational minds with the ability for abstract thought. Same thing, IMO.)
Vast areas of practical agreement flow from our shared starting point: The necessity for a morality based on individualism instead of collectivism, the necessity for the non-initiation of force or fraud, yet the acceptibility (or even necessity) for retaliatory force & fraud against violators. So again: Why fear evolution?