The atheist prides himself on his feelings of fairness and empathy but refuses to acknowledge the culture from which he has inherited these attributes. Such notions are as prevalent as the air we breath (thanks to Christians), but at one time in history they were not.
Atheists frequently point out just how culturally, politically, and socially conditioned religious beliefs can be. Religions that are supposed to be based on revelations from an unchanging divinity about absolute standards of conduct end up teaching and promoting attitudes that look remarkably like those already fostered in the broader political and cultural climate. It's rather curious, then, for atheists to be accused of being ignorant of the cultural influences operating on themselves.
In principle, there is nothing impossible about the accusations being made in the above myth. It's certainly possible for individual atheists to not recognize the degree to which their attitudes, behaviors, and standards are dependent upon the culture around them. This cannot be claimed about all atheists generally, or be attributed to atheism itself, without significant proof — but people promulgating the above accusation do not provide that evidence.
In my experience, atheists have no trouble acknowledging how much we benefit from and derive from our culture — it's Christians who refuse to acknowledge how much culture, which isn't 100% Christian, influences them. Yes, Christian traditions have had an impact on America, American culture, and of course atheists living in America today. No atheist can deny that, but this isn't what Christians are usually trying to claim. Instead, they try to claim that without Christianity, there would be no empathy and morality, and there is absolutely no basis for such a delusion.
Much of what passes for Christianity today seems to be more culturally determined than scripturally determined. This would mean that Christian churches are far more political institutions than they are religious ones. What Christianity "is" is what Christians do, and what Christians do goes far beyond the alleged teachings of Christianity. This is hardly surprising since Christians are not only Christians, but also products of their cultural, social, and political environments.
Some even go so far as to treat those environments as media of communications from their god. When interviewed about her beliefs regarding homosexuality, Betsy Meisensahl equated her "gut feelings" with the desires God. She then decided that if she were wrong in treating homosexuality as sinful, God would communicate this to her via her cultural surroundings: "Knowing what I believe about God, if that's something he's trying to change my mind about, it'll keep coming up. It'll be something that sticks in my mind, and it'll be something, maybe all of a sudden there'll be news stories about this. I'll pick it up in magazine articles, and I'll be overhearing it in conversations. It'll just keep coming up in one way or another."
It's not often that religious believers will explicitly admit that they treat their culture as a means of receiving divine revelations that is effectively on par with their holy scriptures. Something much like this occurs in the background for many — if not most — believers, though, because even when they are focused just on scriptures, their interpretations are conditioned by their cultural, social, and political environments. This is why Christianity is not only compatible with, but has in fact promoted, so many different and even contradictory social, political, and religious positions. This is a historical fact and is undeniable.
Christianity is different from one era to the next, from one culture to the next. Christianity as Americans today practice it is different form the Christianity practiced in colonial America, and both are different from the Christianity practiced in present-day South Africa, 19th century Japan, and medieval France. None of those manifestations of Christianity is any more “true” or “genuine” than the next. All are equally Christian and, by being a Christian, a person is complicit in what they taught.