I think if everyone was Atheist, Most people will not have a base for whats right or wrong. Morality is there but applies to good natured people as far as i can see. If its in your DNA to be a bad natured person , there is no base to stop you from committing misdeeds. One can bring in law but people with no base to decide whats right or wrong will write the law. I cant imagine the outcome of such a world. Reminds me of the movie Equilibrium (2002).
"No one saves us but ourselves. No one can and no one may. We ourselves must walk the path" - Gautama Buddha