There is nothing subjective about this. Solitary confinement is not torture. That is fact.
There have been numerous challenges over the years, and while various courts- including the Supreme Court, have found individual cases where specific jails/prisons have acted inappropriately, Solitary Confinement as a practice, has never been found to be unconstitutional. That is fact.
Solitary confinement is a structured, and carefully managed program used to deal with problem inmates, it's not Shawshank.