Let's go one hypothetical step farther:
For the sake of argument, let's say Jesus never actually existed, but First-Century Jews invented Him and used His story as a parable.
It's been 2,000 years, and atheists are STILL using the moral principles and values espoused in this "mythological parable."
Atheists still haven't come up with a better moral system than the Golden Rule or the total equality found in Galatians 3:28.