Atheism, a dangerous idea?

The world has many religions. If there is no morality without God, then should we believe that morality doesn't exist in any part of the world until it converts to Judaism or one of its offshoots? The ancient Chinese religious triumvirate of Confucianism, Taoism, and Buddhism wasn't based on Christianity. The Greeks had democracy, civilization, philosophy, and science long before Jesus was born. The Egyptians built a thriving civilization more than four thousand years ago. The Romans built an Empire without any help from Jesus or his God. Tribes and civilizations flourished throughout Africa, Australia, South America, North America, and islands all over the Pacific Ocean. All these places had different religions, different customs, different languages ... but they still shared certain moral concepts. Murder was considered immoral. Theft was considered immoral in all societies too large to function as tribal collectives. It was considered noble to help another, and contemptible to hurt others for the sake of personal gain. Honesty was praised. Deception and betrayal were vilified. Governments and gods didn't always obey these laws, but philosophers in all these places somehow found a way to come to similar conclusions. The question that fundamentalists ignore is: if morality flows from God and God alone, then how did this happen? Given the enormous differences in religious beliefs between all these cultures, how did people independently arrive at similar conclusions all over the world, with regard to murder, betrayal, theft, and altruism? Could there (gasp!) be a moral standard out there which doesn't require God?