Just because it is bad is no reason to make it illegal. I live in San Francisco. We have plenty of drugs. But the most pathetic characters on the streets, and believe me we have a world class zoo of disfunctional people here, are actually the hopeless alcoholics. For them plain rotgut is filthier than pot could ever be. And yet ? Can anyone make a reasonable case to ban alcohol ?
And we can go on from there.
The cost in civil liberties and excess government is far greater than the downside of pot could ever be.
Our ultimate problem is a God-vacuum.
Banning the junk that people use to try to fill it is a poor, poor second-line, band-aid response.
If we spent on dedicated evangelists what we spent on drug police, our drug problem would (scientific wild arse guess) dwindle dramatically in but a couple of years.