I completely fail to see how the evolution of our sense of morality (assuming it is evolved) disproves the existence of absolute objective morality. That's equivalent to saying that because we are evolved to discern truth from falsehood, there is no such thing as objective truth.

Thanks, kjmtchi. I don't really follow your reasoning. You say "morality is about making optimal choices", but then end the sentence by saying it's "not about discovering the 'fact' of which choice is correct." To me that is a contradiction. Is the optimal choice not the correct choice? How do you think those who believe in an objective morality make their choices? Isn't it also about finding the optimal choices, taking into consideration different parameters? What makes your parameters reasonable and their parameters unreasonable?