Those people that see this as a shallow way of life I genuinely pity. It's not uncommon for a theist to believe that since atheists follow no religion, they have no basis for ethics. Atheists are generally good-hearted people, just like theists generally are. Our lack of belief in an afterlife gives us all the more reason to live our current lives to the fullest and coexist peacefully. No, we do not need a belief in god or a religion in order to have ethics.
Ethics can come from elsewhere.
They can be derived from logic, for example, or they can simply come from our compassion. The Golden Rule Treat others as you wish to be treated. It has been around a lot longer than Christianity. Many different religions have had this rule in some form or another. You don't need to be a religious person to recognize the benefit of such a belief.