Atheists insist that they can have morality without God. The standard for right and wrong, they tell us, is human flourishing, or empathy, or usefulness, or some other such vague idea. But then they are faced with the problem of defining those concepts, and applying them to real, difficult, sticky human situations. People judge ideas and actions quite differently, so expecting consensus about much is unrealistic. Argument then turns to force, for someone must enforce this morality. Political power is needed to enforce the judgments of some people over others for the good of all. So, might makes right, and we are right back where we started.
C. S. Lewis opined on something similar 65 years ago:
If we ask: “Why ought I to be unselfish?” and you reply “Because it is good for society,” we may then ask, “Why should I care what’s good for society except when it happens to pay me personally?” and then you will have to say, “Because you ought to be unselfish”–which simply brings us back to where we started.
I am not saying that atheists are not or cannot be moral. There is just no compelling reason to be moral rather than immoral.