Hep C can bring slow unpleasant death. A friend's Mom died of Hep C, years ago obviously, who had none of the behavioral stuff by which many get the virus. She got it via blood transfusion during a surgery. Hep C is seriously nasty.
The basic argument the inmates are making is that a 10 year sentence (or similar duration that would not take the inmate beyond the natural human lifespan) should not be a death sentence. Not giving a well known and effective treatment for their disease would have that effect and, they contend, would constitute cruel and unusual punishment.
Whether or not one favors that argument, it is not as frivolous as inmates suing for meds and surgery to effect a sex change.