This question is actually better than it at first appears. Atheists will immediately respond that the recognition of their argument would lead to people living their lives as they truly wish, not ‘controlled’ by religion or fear of gods, and religious based conflict would stop. We would finally be ‘free’ to live in peace and we would go from strength to strength unrestrained by ‘artificial’ barriers. Utopia. But they rarely take the next logical outcome of throwing away an ultimate authority and throwing away purpose: there is then no reason to act in any kind of ‘good’ or ‘bad’ way, and everyone would do what was right in his own eyes (see the Book of Judges for what happens when this is the case). Neither would we have justification for the government and law which puts restrictions on ‘bad’ behaviour. We can see the beginning of this kind of thinking in the last century with the courts having no real authority to condemn anything, instead relying on causes outside the control of the perpetrator like genetics, or up-brining, or mental illness. They can’t call it morally deviant, there’s no yardstick to do that with anymore. Thus, instead of the atheist’s utopia you actually get something worse. What the atheist can’t see or doesn’t want to see is that their utopian vision is actually dystopian.