How so? You make an assertion with no substantiation.
Your claim doesn't make your statement true just because you've voiced it.
Please provide something which verifies your assertion else your assertion is merely your opinion and you should state it as such, to wit...
In my opinion solitary confinement with zero human contact is Cruel and Unusual punishment.
Actually, its been pretty well proven solitary confinement has detrimental effects on the mental health of people who are in solitary confinement for extended periods of time. Look it up.
Furthermore, your statement is illogical on its face as he would, of necessity, have to interact with guards every day.
It is human contact, though obviously not the sort he desires.