To which point are you referring: that morality is defined regionally or that if there is no God then there is no moral superiority?
There is of course no moral superiority in the way that you're using the term. The only moral superiority comes from that which society creates and venerates.
In the beginning of the bible, it was ok to sleep with your sister. In later parts it became a sin. In early parts of the bible, it was ok to keep and trade and reprimand slaves. In later parts, they started shying away from that.
Why? Did an all-power deity deicde on a whim that the rules he created were no longer applicable? Or did maybe, just maybe, the more modern people who were rewriting and editing the bible realize that society at the time had become less and less accepting of elements in the bible? Therefore, in order to retain the faith's strangehold on the populace, they had to move the moral goal posts?
If you (or anyone) wants to be religious, you're best sticking with your "Everything happens for a reason, no one can know god's will argument". It is quite shallow, but you can still fool the simple people with it. Everytime you guys try to make headway into the educated groups, you fail miserably.