> Do you see the trouble with the logic here?

I think you misunderstood my comment. The second sentence was not intended to be an argument or justification for the first sentence. The first sentence stands alone: I think it's unprincipled to ban children from drinking. The second sentence is merely a corollary. Also, I think that legalization and the introduction of adult supervision would ameliorate some of the problems associated with youth drinking, would "moderate" it to some extent.

My view is that the government should not try to be a parent, should not restrict personal freedom, not even of kids, except in so far as one's exercise of freedom harms others, and even there it has to be significant harm, e.g., you can ban violence but not hurting someone else's feelings. The drunk driving laws, which apply to all ages, may be justified by the known role of drunk driving in car crashes. The same principle apples to public smoking bans: the issue is not the first-hand smoke, which is your own business, but rather the second-hand smoke, affecting people who choose not to smoke.