Man is not meant to be alone, at least exclusively alone for years at a time. If anyone should doubt that, try to sit in a room by yourself for 16 hours without audio or visual stimuli. It's harder than you might think. I do think some time alone can be a good tool for reflection, maybe up to ~3 hrs or so. But putting a juvenile in solitary confinement is probably not a good idea for their development.
I respect your viewpoint. I guess I just feel no shred of any feelings towards juvenile deliquents. But remember, I was bullied as a kid and grew up around policemen. My thoughts at 11 years old were "I hope they get run over by a bus". My thoughts at 27 haven't liberalized.