Here is what atheism (not atheists) says. Two brothers help an old lady with bags of groceries to cross the street - molecules in motion. Two brothers perpetrate the Boston Marathon bombing - molecules in motion. Even most atheists do not believe these arguments of atheism.
Atheism has some ad hoc explanations for our sense of morality. Must be evolution. Or, societal indoctrination. But none of these explanations affirm morality. It’s easy enough to say “I will ignore the evolutionary imprint that controls other people.” Or, “I will ignore societal indoctrination and do my own thing.”
Helping a old lady in need IS good. It’s not just that it SEEMS good to some people. The Boston Marathon Bombing WAS wrong. It’s not just that it SEEMS wrong to some people.
If you believe, as I do, that some actions really are good, and others bad, it opens up a lot of questions. Why is it good or bad? Why do we think it is good or bad?
I don’t think atheism has satisfactory answers to those questions.
They would say itmboils,down to “it makes me feel good”, ie personal happiness, self esteem, and that releases endorphins and other good chemicals in my body for my benefit.
Everything has to have a self centered reason under their worldview.