I don't feel like its fair to say "well sure, the stated goal of prisons is to rehabilitate, but they're not doing that now, so why would we even pretend like that is their mission anymore?"
It's like saying, "The war on drugs is to protect our children." Even if that's the official mission & goal statement, I would scoff at anyone who said that to my face and proceed to explain to them what a ridiculous farce it is.
So when someone makes the statement "USA's Prisons are for rehabilitation" to my face, they'll also get the same scoff from me followed swiftly by an explanation of the ridiculous ineffectiveness of it all.
Both of those mission statements are so far divorced from reality that I could not let them go unchallenged in any conversation within earshot. I'd have an overwhelming urge to verify that the person who made the statement understands how much of a failure those missions have been and I'd suggest that the real mission, for anyone actually paying attention, is that of oppression & profit.
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preemptive: And please don't anyone reply with that tired rebuttal of "Only 8% of prisons are for profit", that's been covered several times ---https://news.ycombinator.com/item?id=8562786
Whose to say that one of the (many) reasons it currently isn't successful is that by feeling disconnected from friends and family it further makes them feel separate from society?