If people were told for sure that God did not exist, then I am pretty sure the crime and murders and adultery would go up 10 fold, it is only fear of God watching us over is keeping them under control.
It is know fact that CCTV cameras cut the crime rate down.
Those who believe that there is a God who is watching our every bad action, and it stops them from doing bad things. But this does not mean men who believe in a God and even those who run religions do not commit crime from time to time.
This was, I believe, one very good reason for organising religions in the olden days. In those days everyone, or almost everyone, really did believe in God and the likelihood of being sent to Hell if they were bad. Consequently, religion did tend to keep people in their places.
Today, however, I'm sure that most criminals do not believe such things, even if they profess to be religious. In fact, I understand that even the Church these days tends to play down or even deny the concept of Hell Fire.