Since you here present utilitarian grounds for traditional morality, you yourself show that even an atheistic utilitarian can accept that your morality is of benefit to society. (And individuals are always apt to see benefit in following the morality of any society with a system of justice, formal or informal.)
BTW, I don't know a lot of people who suffer from "despair," and I doubt very much that despair or major depression or any such thing correlates much one way or the other with belief in evolution.
You are finally getting my point. Materialism destroys the basis of a good society by destroying belief in God. So, like the saying went, materialism plants the seeds for the destruction of us all. Now this can in no way be called progress, or advance or helpful to the human species. Therefore the scientific materialism which evolution proposes is false. It does not lead to betterment, it leads to destruction. So again we see that truth and morality go together.