The Argument from Atheism

Reppert's third argument against moral objectivity will obviously not be acceptable for the theist:

III. Argument from atheism
1. Probably, unless there is a God, there cannot be objective moral values.
2. There is no God.
3. Therefore, probably, there are no objective moral values.

Even among atheists, (1)  is not necessarily accepted. This argument doesn't seem to gain any traction.