The fool says in his heart, “There is no God.”
They are corrupt, they do abominable deeds,
there is none who does good.
2 The Lord looks down from heaven on the children of man,
to see if there are any who understand,[a]
who seek after God.
3 They have all turned aside; together they have become corrupt;
there is none who does good,
not even one.
4 Have they no knowledge, all the evildoers
who eat up my people as they eat bread
and do not call upon the Lord?
5 There they are in great terror,
for God is with the generation of the righteous.
6 You would shame the plans of the poor,
but[b] the Lord is his refuge.
7 Oh, that salvation for Israel would come out of Zion!
When the Lord restores the fortunes of his people,
let Jacob rejoice, let Israel be glad.
This is a rather depressing view of humanity. There is none who does good, not even one. Those are not words that go over well in a culture that says human beings are basically good and that when we do wrong it is an aberration. David see humanity as basically bad and it is unusual when we do good. As I read the headlines I am forced to agree with David. YEs there is good that happens in the world but if we are basically good, how can you possibly pass off ISIS, Al Shabab, human trafficking, gang raps across India, Boko Haram kidnapping hundreds of young girls, mass shootings and more as isolated aberrations? Especially when those are only one days worth of headlines.
I suspect David is right. The human heart is deceptive and wicked. We are prone to violence. We are prone to abuse of others. We are this way because even if we do not say there is no God, we act as if there is no God. We put God in a box and lock Him away, even if only for the time it takes for us to sin. Why do we think God is unaware and will not act? As he so often does, David closes this Psalm with a reliance on God that the God of all creation will be our refuge and will restore the fortunes of His people. Then we will rejoice and be glad.
But before that comes to pass I must wrestle with my own sin and rebellion. I have to come to grips with the fact that my heart is often wicked and deceptive. I am a far greater sinner than I want to admit. But the Good News is that God loves me far more than I could ever hope for. I cannot rescue myself from a deceptive heart, but the Lord of Glory, the God of Zion, will bring salvation and be my refuge. Oh Lord how wonderful you are. Praise your name. I rejoice that you are God and I am not.
Dan Lacich: Provocative Christian Living 
I remember learning the concept that we all born sinful while sitting under your teaching. It was a hard concept to accept, but so important.