They are both largely incoherent in that debate because they both think "the right next move" is to test "free will" against their notions of morality. Morality has nothing to do with free will. If you consider morality important, then you might care about free will within your moral framework; but you can debate free will without any notion of morality, and neither of them can see that. (is - ought, which they both are aware of)