There is a bus ad campaign that will run throughout the Christmas season in the DC area whose aim is both to recognise the atheists and agnostics who sometimes feel left out during the holiday season as well as to "plant a seed of rational thought and critical thinking and questioning in people's minds."
It is one thing for atheists to claim that God does not exist, but it is quite another to claim that it is rational to be good for goodness' sake if God does not exist. If God does not exist, there can be no basis for objective morality, and if there is no objective morality, then it is impossible to condemn any bahavior as objectively, morally wrong.
Many atheists and skeptics do not think this through carefully, and so they respond to this arguement in amazingly irrelevant ways. Is the theist claiming that theists behave more morally than non-theists? Is the theist claiming that non-theists cannot recognize morality without believing in God? The ansnwer to both questions is no. All human beings recognize the validity of morality. The theist's claim is that we all recognize morality because we live in a universe that comes already packaged with rules of behavior. All human beings, regardless of what they believe about God, at some point recognize that there are things that are really moral and other things that are really immoral.
The recognition itself may have a lot to do with our upbringing, genetic make-up, but what is recognized (i.e., morality) is objectively true regardless of our genetic make-up, upbringng, social conventions or personal decisions. That is impossible to account for from an theistic persective.
For more on atheists and morality, see this essay.
