I see this argument an awful lot, prevalent despite its reliance on an elementary mistake: "People who smoke dope are losers and commit crimes to fund their habit." Implicit therein is an underlying assumption is that the dope made them losers, as though to suggest that getting rid of the dope would solve the problem. Let us consider the typical jobless loser who smokes dope, shall we?
Which came first? Would these people be upstanding or even particularly functional citizens if there were no dope, or even if there were no beer, percocet, oxycontin, mouthwash, hairspray mixed with water*, or whatever? How and to what extent do these people differ from, say, drunken hicks who can't hold down jobs, fat housewives who blow their money at casinos, grandmothers who sit in front of Home Shopping Network all day, or obese, numb-minded teenagers who spend most of their waking hours in front of World of Warcraft? That a person imbibes too heavily in a given chosen means of the pursuit of self-pleasure is more often not the cause but the symptom of their being a useless tosser to begin with.
Sure, people shouldn't be giving weed or such to kids, but there's not much use in acting like somebody who spends all his time doing nothing but pleasuring himself--whether with drugs legal or otherwise, slot machines, video games, or a bottle of Vaseline--and stealing out of unattended purses to gamble, drink, or smoke in lieu of working is totally without blame and would never have become such a pathetic git if only that evil stuff hadn't corrupted his poor, fragile mind.
*"Ocean", for the curious. This enjoys some popularity on Navajo reservations.