Quite. It is a perfectly coherent possibility that the moral instincts given to us by evolution are broken in some way, so that studying morlaity form the evolutionary perspective does't resolve the "what is the right thing to do" question at all[...] How can EY be so open to the one possibility and so oblivious to the other?

He has attempted to address this issue in the Meta-Ethics sequence, although I find his points on this specific matter very confusing and I was very disappointing with it compared to the other sequences.