It does irritate me when people see prison as some kind of therapy session that's meant to fix people. It's not, it's a punishment. That's it. The government could crack down on all the stereotypical horrible stuff that goes on in higher security prisons, but it doesn't (while maintaining enough of an effort to prevent outrage) because it makes prison an even more undesirable place to be. Don't do bad stuff, you get to live with an intact rectum. Simple. You come out of prison, don't want to go back. Okay, don't break the law. It's meant to make people realize breaking the law isn't worth the horrible consequences.
As for druggies, though, I'd say rehabilitation is the better solution. They're doing this crap out of desperation. Your brother robbed someone for drug money, I'd say he needs to go to a secure correctional facility (they might send him there, I don't know). If he is a druggy, rehab is the best thing for him. Too bad it got made mandatory when he was caught, and it might come back to bite him when he comes out, but that's life, I'm afraid.