What I meant by that statement was that Atheists tend to dismiss our sense of right and wrong when it has a religious context. In my experience, when you tell them that you "believe" something, they view your belief as irrelevant.
I suppose that when it comes to matters like coffee and blood transfusions, the moral beliefs as such do spring from a religious source.
However, for we atheists, religious sources are not the origin, but the continuation of the habits, thoughts, and opinons of people. Further, when people no longer accept a religious proclamation as valid personally, they find/invent a "legitimate" way to disregard the religious instruction. A good example is the shellfish and homosexual behavior of a certain type are both abominations in Leviticus, but one has been discarded while the other has been expanded, due to the subsequent preferences of the believers.
moevillini, I don't know if I would describe morals as arising in a social contract (something exterior to humans), as much as our sense of empathy that most members of our species possess. The social contract, to the degree it exists at all, is a codification of the varying degrees/types of empathy into a social framework.