I am always surprised how often atheists of even the most sophisticated variety miss the mark when it comes to discussions on morality. The question really isn’t whether a particular behavior can be explained or understood ‘naturally’, the question of the ages is can human behavior rise above nature?
Interestingly Jesus addressed that very question when He said:
“You have heard that it was said, ‘Love your neighbor and hate your enemy.’ But I tell you, love your enemies and pray for those who persecute you, that you may be children of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. If you love those who love you, what reward will you get? Are not even the tax collectors doing that? And if you greet only your own people, what are you doing more than others? Do not even pagans do that? Be perfect, therefore, as your heavenly Father is perfect.
We can easily explain the way Nazi’s treated people via naturalism, but a transcendent morality is necessary to explain the actions of the people of Le Chambon-sur-Lignon.