It is a common question of the religious, particularly the Christian, to ask when confronted with the atheist, “what keeps you from killing, raping, and doing whatever you want?” I’ve encountered this response enough that I think that the religious adherent, particularly the Christian, honestly believes that the source of their morality is their God and their Bible. It’s interesting that the Christian doesn’t consider that morality exists cross-culturally and is evident in human history prior to Christianity. If morality is informed by the Christian God, then why does the Muslim profess moral principles? Why does the Hindu? Why does the member of the Navajo nation? And, what about the West African tribesman? Are these people immoral, deliberately violating moral principles? Are they amoral, living without any concept of morality?
The short answer to the Christian who asks where the atheist’s morality comes from is that it comes from the same place as that of the Christian: human experience and the intuition of right and wrong. The Christian attributes this understanding of morality to their religious upbringing, but studies have demonstrated that morality is understood beginning at age 2 and 3 as toddlers begin understanding that hurting others is wrong . Of course, it’s easy for the Christian to attribute this understanding among their children to their Christian lifestyle, but that doesn’t explain why the children of non-religious families have equal understandings of right from wrong.
People express morality in a variety of ways. For many, racist behavior goes against their moral principles –that principle being that racial discrimination is wrong; this might inspire someone to be careful that they aren’t giving the appearance of being racist and plan actions accordingly through moral reasoning; to use a racial slur or not is to employ the moral concept of “right from wrong;” we can criticize the decisions others make on the basis of racism, forming a moral judgment; and by admitting to ourselves that a racist should others fairly in spite of skin color differences, we admit to having moral feelings.
I use the “racist” example on purpose because it was only a few short years ago in American history that the same religious doctrine that informs Christian morality also informed many Christians that racial oppression was a morally correct concept. Indeed, this same doctrine once considered the Navajo nation, along with the other 500 or so aboriginal nations of people that populated the North American continent to be godless savages, exempt from the “golden rule,” which suggests that one treat others as one would wish to be treated. So my short answer above may actually be wrong in hindsight: Christians don’t obtain their morals necessarily from the same place as the atheist or the humanist.
I’ll not quibble with the fact that the morality taught by the mythical figure, Jesus Christ was, for the most part, admirable. “What would Jesus do?” is a powerful statement (it really is a statement more than a question) to most Christians, but when compared with supposed “Christian values” and “Christian morals” of modern Christians, it fails. Being Christian doesn’t guarantee moral behavior.
Some of the most heinous crimes committed include those committed against children, bringing to mind the pedophile priests of Catholicism. But lest the Protestants think they’re exempt, let us not forget the Houston mom that drowned her 5 children one-by-one. And what did Andrea Yates tell her prison psychiatrist?
“It was the seventh deadly sin. My children weren’t righteous. They stumbled because I was evil. The way I was raising them they could never be saved. … Better for someone else to tie a millstone around their neck and cast them in a river than stumble. They were going to perish.”
If I were a Christian apologist, I’d argue that I’m cherry-picking a few isolated cases and that Christians are human and, in spite of their strong moral values and training, even they can be afflicted with evil. But, how then, does the Christian explain the data that indicates that the very immoral concepts that Christians are most vocal about are often the ones they have the most problems with? I’m speaking of abortion, murder, and the sanctity of marriage among others.
Abortion rates among religious societies are significantly higher than that of secular ones. Some of the highest rates of abortion are in the United States (23 per 1000), one of the most Christian nations on the planet. In places like Western Europe where religiosity is low, abortion rates are low (11 per 1000) . Homicide was, likewise, positively correlated to religiosity with the United States leading the world, per capita. In the U.S., the homicide rate exceeds Western Europe’s by 4 to 1 and Japan’s by 7 to 1 . With so many Christians in the United States openly objecting to same-sex marriage based on the “sanctity” of this institution, one might expect them to be setting the example. However, U.S. Divorce Rates by religion reveal:
Born-again Christians 27%
Other Christians 24%
Atheists, Agnostics 21% 
Why don’t Christians, or for that matter, Jews (who also frown upon the practice of divorce), have lower rates of divorce than atheists and agnostics?
The answer is that morality is a human concept, informed by human experience and human intuition. To the humanist-atheist, there is no escape-clause of getting forgiveness or atonement from a deity for immoral acts. We act and behave as though life is sacred not because it was divinely given until some mythic afterlife occurs, but because it is the only opportunity we have to make a mark on this planet and our actions affect those we come in contact with as well as those that follow us. We don’t require the threat of punishment by an invisible deity or an eternity of torture in a “hell” to treat other humans with dignity and respect. Nor do we need the motivation of eternal life to seek to better our world and improve the lives of others if we’re able.
 Tisak, MS & Turiel, E (1984). Children’s conceptions of moral and prudential rules. Child Development, 55 (3), 1030-1039.
 http://www.guttmacher.org/pubs/journals/25s3099.html (1999 data)