Ruse: The evolution of Morality shows objective moral values don’t exist and makes our belief in such objective values unjustified.
Skarsaune: Not so fast, not only does evolution not even remotely entail the non-existence of moral values, but here’s one way in which the story you just told us about the evolution of morals can be true while allowing us to be justified in continuing to believe in the existence of moral facts.
He’s not saying anything about whether moral facts actually exist or not because that’s not the point of the paper. The point of the paper is to show why evolution just doesn’t threaten moral realism. Whether moral realism is true or not is an altogether different question tackled in different books/publications.