I'm actually not arguing for an absence of punishment, but rather against punishments whose only end is retribution. Things like solitary confinement, mandatory minimums, inhumane conditions, forced prison labor and more, all very normalized within the US criminal justice system, are all suspect practices whose only definite result is an increase in suffering. Punishment could be educational and rehabilitative (and still austere and undesirable, without being purposelessly cruel).

Deterrence is commonly cited as a justification for retributive justice, but does it actually work that way? We obviously don't have a great control since we've had this system of justice for centuries so it's hard to imagine a radically different system. But the data we do have suggests that increasing the severity of punishments does little to increase the deterrence factor [1]. So we could likely make our criminal system significantly less cruel without reducing the degree of effective deterrence.

Also I wasn't arguing for moral judgements of judges and prison guards for working within the current retributive justice regime (though those who wantonly exacerbate the cruelty of the system should certainly be judged for doing so). It's a systemic issue that retribution and cruelty are the implicit end goals of the US criminal justice system.

[1]http://scholarlycommons.law.northwestern.edu/cgi/viewcontent...