I don't see much of an issue in it, at least the pot aspect. Obviously, with limited law enforcement and correctional facility resources, emphasis should be placed on violent crimes and serious drug offenses, not simple possession.
Should a guy running around with a few kilos of heroin in his trunk get jailed? I think so. But should some kid with a gram or two of weed in his pocket get the same treatment? I don't think it's the same thing.
On the other hand, I don't think cocaine and heroin should be treated as nonchalantly as pot. I've met several guys who did a lot of pot in high school and college, and most of them were fully capable of getting good grades and keeping a normal mental function, while toking up on the weekends. But I don't think those harder, more addictive drugs lend themselves as well to casual use. A fratboy who gets stoned with his buddies and then eats a bag of potato chips while watching a dumb movie isn't much of a threat to the safety of others, as long as he isn't driving.