Your "man's law rules supreme" "morality" results in blacks being forced into slavery and Jews being forced into ovens.

Premise 1: If there is no God, then objective moral values do not exist.
Premise 2: Objective evil exists.
Conclusion 1: Therefore, objective moral values DO exist.
Conclusion 2: Therefore, God exists.

A-theists affirm premise 2 by pointing out how objectively "evil" Christians and the God of the Bible are.

Therefore, by identity with Premise 2, Conclusion 1 is achieved. Theref ore, by Modus Tollens of Premise 1 and Conclusion 1, Conclusion 2 is achieved, and God exists. So, when you talk about how objectively "evil" Christians and their God is, you are unwittingly acknowledging His existence.

A-theists affirm Premise 1:

“In a universe of blind physical forces and genetic replication,
some people are going to get hurt, other people are going to get lucky, and you won’t find any rhyme or reason in it, or any justice. The universe that we observe has precisely the properties we should expect if there is, at bottom, no design, no purpose, no evil and no good, nothing but blind, pitiless indifference— DNA neither knows nor cares. DNA just is. And we dance to its music.” (Richard Dawkins, River Out of Eden: A Darwinian View of Life (1995))

“Let me summarize my views on what m odern evolutionary biology tells us loud and clear — and these are basically Darwin’s views. There are no gods, no purposes, and no goal-directed forces of any kind. There is no life after death. When I die, I am absolutely certain that I am going to be dead. That’s the end of me. There is no ultimate foundation for ethics, no ultimate
meaning in life, and no free will for humans, either.” A-theist William Provine

As an a-theist, you don't get to criticize ANY morality - objective morality is just an ice cream flavor to you. By using the objective term "morally repugnant," you are actually admitting to an Objective Moral Standard and therefore, you are unwittingly affirming the existence of God. You can't have it both ways: if God does not exist, then all things are permissible. If you don't like that fact, take it up with your "pope" and "cardinals" of a-theism. :-)