Nonsense. Any rational creature can discover common societal norms that when enforced bring a joint mutual benefit. You might personally find that too morally hollow for your tastes, but it leads to a set of laws similar to those discovered by the biblical writers.
Really? Any rational creature?
Marx, Lenin, Stalin, Mao, Pol Pot, were these not any rational creatures?
Perhaps the only problem with atheistic philosophy is that TRUE atheistic philosophy has not yet been tried?
I don't know why so many wish to argue that morality is not inherently logical.
Buddha figured it out, and said nothing of God.