Why 'should' atheists be moral?

[Mystic]

Interchange "divine" with "subject" or "ego" and I'm on board. But as it stands, in however you use word the divine, I don't quite grasp how value is to be derived... simply because it's valuable? Seems redundant.

It's like droplets from an infinite ocean or rays from infinitely bright light, the droplets or rays in this case get their nature from the origin, but they aren't exactly the origin either. It's a descent from the absolute high (absolute) to a finite existence and division.