Of course, MADD responded with castigations of fear and hyperbole.
ChooseResponsibility.org has good, frequent updates weighing in on statistics and moral arguments for lowering the drinking age. I found this particular post interesting:
Research predicts that only two out of every 1,000 occasions of alcohol use by individuals younger than 21 result in arrest. Even with a five-fold increase in spending, enforcement officials would only raise the chances of catching underage drinkers 1% of the time.