There is no morality without God.
Untrue. There one can define all sorts of moral systems based on ... well, whatever principles one decides are important. "Might makes right" is one, for example.
The distinction is, rather, the what basis by which can one say "that is wrong," or "this is the right thing to do," and have it mean only one thing.
At root, the questions boil down to these two:
1) Do you propose that true "morality" is based on a set of fixed and immutable principles?2) If so, on what basis do those principles come into being?
It's at that point where one gets into the necessity of God, if one is to assume that moral principles are absolute, rather than relative.