how can atheists use the words "moral" and "immoral"?

people say (says christopher hitchens) "how can you talk about morality and say something is immoral if you reject god and the bible--the source of morality, the source of the ten commandments?"

well, atheists can, for at least two reasons:

* the bible/yahweh doesnt own morality. just look at all the non-believers in the world who do good, not to mention people in other cultures who may never have heard of yahweh or the bible!

* it's using the language of theists so they understand what you are talking about. speaking to them on their own terms.