Followers of Abrahamic religion (christianity, islam or judaism) believes, by following the correct religious doctrine you will enter heaven in the afterlife, if not you will be consign to hell. This mechanism raise the ultimate cost and benefit of good and bad to infinity. Without it there is in the long run (death) no cost nor benefit to acting morally. This is perhaps what fear the Abrahamist about atheists the most. Not only do the atheist deny the existence of heaven and hell, they consider the very concept of afterlife to be complete nonsensical.
I suspect that there are closet-atheist-elitist (CAE) who denounce atheism and promote religion because while they are comfortable with themselves living without heaven or hell, they are uncomfortable with others doing the same. These CAE fear the freedom of knowing the ultimate cost and benefit is zero may lead to nihilist social unrest. They imagine nightmare of nihilists going around raping and pillaging, doing whatever they want with completely disregard for other people, and if thing turn for the worse, either because they got caught committing crime or whatever they can just kill themselves to set all balance to zero.
I as an atheist obviously do not subscribe to CAE’s fear. I am convinced that human internal moral compass develop via evolution and the incentive mechanism of modern legal institutes are very effective. To the contrary of CAE’s logic, if ultimately the cost/benefit is zero after death, than the only cost/benefit is that will affect you when you are a life. It does not make leading a life of crime more attractive, it make it less so.
While its extremely difficult to have a watertight demonstration of correlation between believe/non-believer and morality/criminality, because we dont have the technology (yet) to read peoples minds to know if they really believe in god or they are just paying lip service. There is at least some evident to suggest that atheism dont necessarily lead to more, but less crime.
More than half of Japanese consider themselves to be irreligious, they also have one of the lowest homicide rate in the world – 0.5 case per 100,000 people. While in the United States, where only 15% consider them self to be irreligious, their homicide rate is 10 times higher than japan at 5 cases per 100.100 people.
Ricky Gervais sums up the benefit of teaching your kids Christianity (he is now an atheist).