I agree with a lot of what a lot of you are saying. I was going to quote, but that would be tedious, so assume if I mention what you've said here it's because I'm agreeing and clarifying, and not because I'm trying to take credit for the idea:
Rehabilitation vs. Punishment is a big thing, and goes hand in hand with the idea of being lesser citizens upon release, and with the idea of people going to prison for ridiculous frivolous charges.
What happens is you get a dude that goes to prison for some stupid minor bullshit, and he goes in a nice, quiet, mostly law-abiding guy, and you've got him in with hardened career-criminals.
And eventually, you release him, and now he's got a felony charge on his record, so any time he applies for a job, he has to indicate that yes, he has a felony. So now, his choice of jobs is severely limited. Jobs are scarce enough as it is for people who are highly qualified in their fields, imagine how hard it would be for this motherfucker to find a job. Suddenly, with a need to put food on the table, maybe for a wife and kids, and then, maybe the idea of committing a crime to try and get some money isn't such a crazy one. Suddenly, it's about all he has left. Stigma associated with being a criminal is a huge factor in recidivism.
Punishment vs. rehabilitation: I have a huge problem with people who ONLY want to treat it as punishment, for several reasons.
The first, Mortlach covered pretty well. Sure, it's easy to say "oh, that guy's a waste of life, don't bother making him better, it'll never work and he's not worth it" because I do the same bullshit to talk myself out of trying anything new or scary. "Oh, I'll just fail, so why try." It's easy to do, because it requires you to do nothing. But if you do nothing, nothing changes, and if you don't at least TRY to change them, it's a self-fulfilling prophecy because they often DO keep fucking up (because you've done nothing) and then you say "see, what a fuckup," ignoring the fact that you are making no logical sense.
The second would be that, OK, if you are hellbent on chalking it all up to punishment, then when punishment is over and a person has served their time, they shouldn't be treated as scum. If you're going to sentence them to a predetermined amount of prison time, then once they've served it CONTINUE to essentially encourage the rest of their life to treat them as subhuman garbage, that's kind of fucked up, because the punishment never ends.
Frivolous charges:
as an aside: I also have a huge problem with the way America treats addiction and mental health. Because there is such a huge stigma associated with addiction, people are less likely to seek help. This is because they know that if they admit to addiction, they are more likely to be arrested for it than to actually receive treatment for it, and they will always have a mark on their record stating that they were/are an addict. They know that they are more likely to be punished than helped, and so seeking "help" is not their best-case-scenario. The idea of trying to get off the addiction themselves becomes more appealing and less threatening, even if never works, because of the bullshit their lives become if they are arrested for it- after that, it doesn't matter if they're clean and sober for 3 months or 30 years, they're always going to have to be that guy that has felony drug charges because they did heroin back then. This ties in with the previous rant, re: rehabilitation vs. punishment- people don't care if you've really rehabilitated yourself or not, they'd often prefer that these addicts were permanently punished via social sanctions, because omg they're just going to start using again anyway. And then their life is shit, everyone hates them/treats them like shit, they can't get a job, and suddenly the idea of nodding out isn't so bad again, because what use is it to get clean if they'll never escape persecution for it?
back to frivolous charges part: so, on that, I think there needs to be a reworking on how addicts and people caught with drugs are treated. I'm not saying nobody should ever be arrested for any drugs, that's not my point at all, but a complete overhaul of how all of it is treated is needed.
And it's not far-fetched to believe that the reason people of color comprise a disproportionate amount of the prison population isn't because they're more likely to commit crimes, but because they're more likely to be charged (unfairly) and more likely to be convicted. They're even more likely to be sentenced to death dependent upon whether their alleged victim was white or not. Drugs associated with people of color led to sentences above and beyond the essentially equivalent white-counterpart to the drug (i.e. crack cocaine vs. cocaine, thankfully in 2010 with the Fair Sentencing Act this disparity was at least lowered).