National Surveys Show that Pot is More Popular in America than in the Netherlands
A real, impossible to ignore counterexample to the claim that the legalization of marjiuana would result in nation of useless stoners is easily found in Dutch society. American policymakers could treat the Netherlands as one big scientific social experiment, complete with tons of useful data, and realize that the prohibiting drugs has almost no effect on use. In fact, surveys conducted in both countries show that people in pot-friendly Holland are less likely to smoke marijuana, despite the presence of legal, hash-bars.
I got this info (as well as a chuckle from an anecdote about a Dutch woman who never had any desire to try marijuana until she visited the United States) from an OP-ED piece in the St. Petersburg Times.