PyramidHead
Contributor
You can still inflict suffering on innocent people not because *they* are doing something we wish to discourage, but because of general deterrence when other people see them punished for the crime. They don't need to be guilty for that purpose.
If we imagine a rapist and murderer, that let's say had the money to live a life of luxury in prison; and this detail could be kept secret, so it would not diminish the deterrent effect for rich people, it would be widely rejected as an injustice if they actually were living a life of luxury. The public would be just as safe. But that's not enough. Or anyway, that people *do deserve to suffer* fits with common moral intuitions.
Those intuitions are wrong unless they can be justified. If the only material benefit to causing someone to suffer (when he has already been removed from society and there is no need to use him as an example) is to satisfy the emotional craving for bloodlust on the part of some segment of the public, then we should take the high road and fix the bloodlust rather than needlessly hurting someone.