Is freewill morally relevant? Yes, freewill is what makes morality possible. I think what you’re really asking is: If we are actually determined, would that make any difference to our justice system? And the answer has to be that it couldn’t possibly make a difference, that essentially nothing matters because it’s all pre-determined, so why discuss it? Harris is sophisticated enough to say that our mental contents, not just our actions, are determined, but this doesn’t change the situation. He will perhaps argue that he was determined to make the arguments that he has made, and that others are determined to respond to them in whatever way they do. But absent from the entire picture is any choice, and without choice there is no morality. The better tactic in arguing with such skeptics on free will is, I think, to point out that they are freezing the concept of causation at the level of mechanistic cause and effect. LP describes this on pages 64–66 (but he does not actually label it an instance of freezing the abstraction).