Its cruel and unusual punishment
Punishment leads to fear and distrust, not discipline. Discipline is achieved through trust and adoption of responsibility.
It's plainly just..fucked up.
If an inmate breaks a prison's rules, they should be punished.
Everybody needs to stop trying to make life better for criminals in prison. If we want criminals to stop breaking the law we need them to fear ever going back to prison when they get out. Conditions should be worse for criminals who commit worse crimes. Criminals who refuse to change on their own in prison must be forced to change or leave society forever. For both the safety of the guards and non violent prisoners, and the safety of citizens on the outside. As for serial killers in Supermax prisons, no punishment is to cruel. They should be glad solitary is as bad as it gets.
If inmates misbehave, they need to be disciplined.
Whilst you may think it's a cruel punishment, please keep in mind that it's very appropriate for a lot of the situations that put them in this situation. Especially when it comes to them misbehaving and putting other inmates health or lives at risk. There could be some situations that don't quite warrant it where it does happen, but that doesn't mean it should be completely abolished.
simply put, if this punishment is removed from prison then the institution becomes a daycare for naughty adults.
Not entirely. Though it does go against the tenth article (i believe) of the bill of rights, it is needed in many cases. I do also believe, however, that it should not EVER exceed 2 or 3 days. It can really pack a punch like an atomic bomb if it ever exceeds that. Insanity is not needed for a lesson to be taught.