[chongli]

view prison as a way of getting revenge on criminals or as a way of trying to reform them

This is the crux of the whole issue. The US is split between the two notions of justice: retribution and rehabilitation. The split seems to largely fall along political lines, which means the argument isn't likely to be settled any time soon.

I tend to fall in the rehabilitation camp but I can see some of the logic behind the other side. At the very least, I recognize that it's better for the state to apply measured retribution than for families to pronounce blood feuds upon one another. Beyond that, I'm at a loss for what to do about cold, psychopathic individuals who seem utterly incapable of reform.

[zeropnc]

Deterrence and retribution are different things. Prison systems with harsh sentences are typically more about sending a message to potential criminals than punishing existing ones.