If the idea behind the punishment of prison is to remove someone from society, shouldn't that be enough? Why is our society accepting and in some cases even enc

If the idea behind the punishment of prison is to remove someone from society, shouldn't that be enough? Why is our society accepting and in some cases even encouraging things like torture, rape, solitary confinement, etc. for prisoners? This status change to nonhuman begins upon accusation so it's not even reserved for criminals. Basically society says it's OK to do anything to the accused and especially to the convicted. In for panhandling or drinking in public? Our society agrees that it's ok for you to get raped, beaten, maybe even murdered. After all, you must have done something terrible to be in jail or prison. Even if you're innocent.