Why 'should' atheists be moral?

[Chad32]

The idea of 'should' only makes sense in reference to values and goals, with can only come from two sources: outside the moral agent (objectively) or from within to the moral agent (subjective). Without values and goals that transcend the individual, like the Good or the True, the moral agent must look to their own desires and needs as the source. Now to transcend the individual one need only go up one level to the community. That move doesn't say from where a community gets its values. Appealing to evolution doesn't solve the problem, since it only applies to survival. You need to be able to show that survival is the ultimate source of value to get near anything objective.

Survival is the foundation of everything else. Without it, nothing else would be possible. People would die, communities would crumble, and empires would fade from existence.