Dostoyevsky declared in The Brothers Karamazov (I think) that "If there were no god, then all things are permitted." This is the usual theistic attitude toward morality. But I think there are several flaws in this rather drastic statement. First of all, it gives free rein to anyone whose belief in God has lapsed for some reason, to engage in anti-social behavior...in fact the doubter may feel compelled to "sin" since that is what is expected of him. And then the atheists would also feel they were excused from societal prohibitions.
What is wrong with social controls being based on respect for each other? This kind of respect is incorporated into buddhist beliefs and practices.
I think a case can be made that morality can be based on something other than belief in God....the buddhists have been doing it for 2,500 years. In their case, the doctrine of karma acts as an impersonal force which deters selfish behavior and promotes good deeds. Also, their belief in reincarnation means they believe every sentient being has been their mother in some previous existence, therefore compassion for all life is generated. These beliefs are reinforced by the practice of meditation, which forces one to examine one's mind and see in vivid detail how selfish one really is, and therefore inspires one to engage in less painful selfless activity.
It does seem that social morality without religious input often leads people astray. But buddhism proves religion can exist without a supreme deity.