The athiest believes what (s)he says is right or wrong, not anyone else’s standard. The Christian believes that God determines moral values and reads the Bible to find them. The muslim believes Allah determines appropriate actions in life and therefore kills everyone who disagrees with him or her.
let me offer a more balanced alternative:
An atheist may choose to subscribe to a codified ethical system created by someone else, which typically lack an appeal to a diving being. For instance they may consider themselves a "Humanist" and follow the teachings of humanist philosophy.
A religious person chooses to subscribe to the codified ethical system, typically handed down from ancient times, which ascribes its ultimate origin as divine. For instance they may consider themselves a Christian and subscribe to the moral codes contained in the Bible and interpreted by their particular sects teachings.
(For the sake of simplicity and symmetry I'm going to take both believers and non-believers at their word and not try to impose external definitions on them ("anyone who says that isn't really a Christian")
I would say that many of the atheists I know have struggled with questions of morality and have reached some clear conclusions. For instance many libertarian atheists view the Non Aggression Principle as very important axiom of their own behavior and look for it in others.
I think many people professing Christianity are functional nihilists, whose understanding of Christian morality is shallow. Many of these people in fact use Christianity to assuage their conscience. Jesus forgives, only belief in him is needed for eternal life.
As Jim's Free Republic Credo thoughtfully posted above says FR stands against "government enforced atheism". The track record for that is truly horrible.
On the other hand the track record of doubting, skeptical, agnostic and philosophical atheist people is not horrible, in fact data suggests that atheists are among the least likely to be convicted of serious crimes (second only to Pentecostal Christians). Here is