JF1, there is a big difference between locking someone up for possession (or even distribution of small amounts or nonviolent crimes arising from addiction), and locking people up for crimes of violence. Violent offenders definitely need to be off the street. i know people who have recovered while in prison serving time for violent offenses, and they would be the first to agree they had forfeited the right to be walking around.
De-criminalizing drugs isn't the same as legalizing them. But I don't see any point in refusing to legalize marijuana. A substantial portion of the population at this point seems to favor it, or at least not be strongly opposed to it.
And I get your point about government programs "enabling" people to continue to use drugs and alcohol, but I still think that the current "war on drugs" is more costly than effective. I don't believe most people who use drugs are deterred by their illegality. I don't believe more people would use them if they were not criminalized. The illegality is what drives up the price, makes it lucrative for dealers, which in turn contributes to the violence and corruption driven by the illegal drug trade. I would rather have addicts able to get their drugs legally than to have little kids getting shot on their way to school by warring drug dealers (a common occurrence in the city where I was working).
If the money being used to fight the "war on drugs" was instead put into rehab facilities and prevention and treatment efforts, I think society as a whole would suffer less.