The Future Of Pot, Ctd

Cowen's response to my last post:

When it comes to marijuana legalization, I believe that the "anti-" forces will muster as many parental votes as they need to, to defeat it when they need to.  The elasticity of supply is nearly infinite at relevant margins.  Legalization may appear "close" for a long time, but in equilibrium it will not spread very far.  The "no" votes will pop up as needed.

McArdle thinks Cowen might have a point:

I'm not saying this happens to every single person who has a kid.  But in my experience, as the kids approach the teenage years, a lot of parents do suddenly realize they aren't that interested in legal marijuana any more, and also, that totally unjust 21-year-old drinking age is probably a very good idea. ... Maybe we have reached the high-water mark of this sort of personal liberty.  As the baby boomers age, they will be less interested in directly exercising their right to smoke pot, which means that even if they still support legalization, they will be less motivated on the issue.  Meanwhile, there will be more people in the electorate with young adult children who they worry about--and fewer young adult children. 
Maybe the kids thing explains Josh's discomfort as well. But again, you cannot help but notice the parallels with gay equality. Prop 19 went down because of scared parents; Prop 8 passed because of scared parents. The question is whether the fear is rational. With homosexuality, it's totally irrational. No kid is going to become gay because gay people have civil equality. But more kids will be less hostile to their gay peers and gay kids will have an inking of a better future.
With pot, legalization could mean more teen consumption. But again, the question is: can we control this more with a legal regimen or by allowing the current situation where most teens can easily get pot, but do so from criminals and with no supervision?