I think there is a profound problem in the discussion of freedom and moral responsibility because I think the idea of desert fits in well with a religious world view like Christianity, and is in fairly serious danger from a secular perspective, which is something worth noticing when you read Lewis's essay on the Humanitarian Theory of Punishment.
But even if Desert drops off the table, if you have a serial killer running around killing people, you want him to stop doing it, you want to deter others from doing the same, and if perchance it is possible to make him a productive member of society, you want to see that happen, too. You also don't want angry people in the community. You have a batch of utilitarian considerations that will probably result in our doing, in many cases, the same things to the person that would have been done if you thought the person was really morally responsible. It's not like we would say "Sorry to see you're killing people, but it isn't your fault, so I guess we've got to leave you alone."
Chesterton wrote: The determinist does not believe in appealing to the will, but he does believe in changing the environment. He must not say to the sinner, "Go and sin no more," because the sinner cannot help it. But he can put him in boiling oil; for boiling oil is an environment.
But, so is saying "Go and sin no more." It may modify the "sinner's" behavior. But as a revelation of some truth about the sinner, I think Chesterton is right. Real sin, real blameworthiness, requires being something more than a biological machine.
In a consistent secular world-view, following that view down the path of materialism/naturalism, I think the whole idea of desert can't be sustained. But there can and will be a lot of conduct on our part that looks and sounds like we're holding people morally responsible. But on close examination, the heart of moral responsibility, an assessment of desert, drops out of the picture.
The link is to some quotes on Chesterton and materialism.