Psalm 53 may have been a popular psalm with God’s people. It is one of those you will find repeated in the book of Psalms (Psalm 14 is another rendition of it. You will also find Psalms 40, 57 and 60 repeated, in part, elsewhere in the Psalter). The sentiment expressed in this Psalm is that of mourning – grief because of those who deny the existence of God.
I doubt seriously that this is a true charge of atheism among God’s people. Instead, it it the charge that God takes no notice of the affairs of the world. Jeremiah tells us about such people in Jeremiah 12:4, but he is not the only one to refer to them.
One doesn’t have to be an atheist to live like an atheist. When our behavior is such that we think God doesn’t see or, perhaps, God just doesn’t care, then whatever our beliefs are, we have embraced the ethic of the unbeliever.
The psalmist sees this attitude as harmful to the people of God, either because of consequential sin, or because he knows such an attitude will bring the judgment of God – a judgment that is not always surgical in its strike. Collateral damage is sure to play a role.
In this psalm you have the words of the mourner Jesus blesses in the beattitudes. This person cares about how God is perceived in the world and by the world and he looks forward to the revelation of God which will bring to a halt the kind of lives lived without regard for the Lord.