I don't enjoy being cruel to convicted criminals. I would much prefer they not commit crime, and that there be no need for the punishment.
>especially given that free will is inconceivable;
I too, have no free will in the matter. I am just a clockwork mechanism, operating as the random universe has not only ordained, but I cannot operate otherwise. Coincidentally, the nature of my mechanism makes me immune to your arguments, and no change in behavior is forthcoming. Fun, huh?
>mass incarceration and poor prison conditions seem to increase crime
Statistics say otherwise. Crime is down across the board the last few decades.
>If we are to have prisons, let's be honest about why they exist: people like them.
I agree. I like criminals being locked away from the rest of us.