The proposition that it is impossible to talk about morality without reference to a moral lawgiver is wrong on the evidence. Humans are moral animals (sociopaths excepted) because natural selection wired our species with the ability to learn and internalize norms. We are not the only moral animals. All social animals need have their own moral "codes" You just have to watch playing dogs with an open mind to figure that out. And, despite the world wars, the 20th century on a per capita basis was the most peaceful in history: see Steven Pinker's book, The Better Angels of Our Nature. The problem is that we are naturally wired for Stone Age conditions and our moral  intuitions do not always serve us well in modern conditions. We now have to work out rules for living together through discourse and reason.  The Moral Lawgiver of whom religion speaks is the voice of our intuition. And, too often, that voice is the voice of angry  tribal gods.