The writer is not stating that there is no God. He is stating that the premise that we need God to have morality is false. Human society intrinsically has to be moral in order to function. It is the model that best works, and when there is an exception, say a psychopath killing women, society will punish that person (whether you believe it is the hand of God or not). The idea that an atheist, or secular, society would irrevocably slide into amoral behaviour is simply illogical.