In issue #82 of Philosophy Now, there is a series of articles on atheistic moral theories. These are categorized as the familiar "moral relativism" and "moral skepticism." These theories deny objective or absolute morality and embrace subjective and relative moral judgment ("different strokes for different folks").
Nevertheless, at bottom, all of these atheistic theories have a common presupposition of human autonomy and, thereby, a teleological (action for the sake of an end) basis for their ethos -- be it the variety of pragmatism, utilitarianism, relativism, errantism, or fictionalism. All of the discussion depends upon man having the ability to be guided by utilitarian goals (an act is "good" based on what it achieves) and ability to choose among alternative actions according to subjective (dependent upon the subject) or relative rules (such as mere societal conventions).
But! Since atheistic monism and human autonomy are antithetical, none of these philosophical discussions are rational. They are irrational at their very core! On their worldview, man cannot make choices, but only acts as he must. Therefore, the teleology that their moral theories assume is merely a phantom.
Of particular note is the article by Richard Garner titled, "Morality, the Final Delusion." Garner bites the bullet and compares the existence of morality with the existence of God. Taking his lead from Richard Dawkins, he is bold enough to say that belief in morality is the "Morality Delusion!" Thus we see that in the end, the atheist makes his bold assertions concerning his metaphysics using the supposed power of "his" autonomous reason. But such "rationality" -- which, again on his worldview, can only be the irresistible effect of matter obeying the fundamental laws of quantum mechanics -- is not reason following resistible fundamental laws of logic. There are no fundamental laws of logic in a universe ruled solely by the fundamental laws of physics.
The atheist's irrational faith in his rational autonomy is the final and only area of philosophy he will maintain to the bitter end. It would be remarkable if Garner would logically assert the concept of the "Logic Delusion!" To assert such is obviously delusion in itself. But it is the inescapable consequence of monism. Such are the pretensions and self-contradictions of atheism.