All rules of conduct are human made. They are the result of requirements necessary for cooperation in maintaining social order. The higher animals, including humans have evolved empathetic and compassionate traits beneficial to survival. Our intellect continually refines these, as circumstance requires.
Ask yourself these two questions:
- What religious rule do you know about that has not or is not capable of having originated from humans?
- If you found sufficient evidence, conclusively proving that a god did not exist, would you develop into an immoral person?