The Moral Argument that Christians don't use, but atheists always rebut

Does William Lane Craig ever say that we need to be believers in God to lead moral lives?

Guess what. He does NOT.

This is from the opening speech to his 1996 debate with Doug Jesseph:

Friedrich Nietzsche, the great atheist of the last century who proclaimed the death of God, understood that the death of God meant the destruction of all meaning and value in life. I think that Friedrich Nietzsche was right. But we've got to be very careful here. The question here is not: Must we believe in God in order to live moral lives? I am not claiming that we must. Nor is the question: Can we recognize objective moral values without believing in God? I certainly think that we can. Rather the question is: If God does not exist, do objective moral values exist?


Yet, when I hear atheists talking about moral arguments, they always assume that the advocate of the moral argument is saying that we have to believe in God to lead moral lives, (and indignantly argue that we don't have to believe in God to lead moral lives) in spite of the fact that Christian advocates of moral arguments, at least the ones I am familiar with NEVER say that.

Why?