Is athiesm good for society?

When we look at Hitler (self and race worship.), Stalin, Mao, PoPot (Cambodia) and all the death and horror from such atheistic regimes, aren't we lucky we have religion to serve as a conscience for society. Mao alone killed far more people then all the crusades and inquisition put together. Add in the other atheist leaders and you have immeasurable amount of deaths (this was only in the last 90 years.) The number of deaths from atheism in the last 90 years makes the deaths from religious leaders pale in comparison.