Think of it with sensibility. We are approaching this like it's taboo, marijuana is not taboo in our culture.
How many tax dollars are we losing to crime? How much money could be made in taxation?
Prohibition was a failure, so is making marijuana illegal. It's a drug that will be used, will be sold, will be grown, until we find some cheap way to synthesize THC in someones closet.
It's the easiest drug for a minor to get their hands on. A person under 19 is more likely to find a marijuana dealer, than to find someone to sell them alcohol.
A quarter of high school students are stoned... What other drug lasts them hours and costs 5-20 dollars? Well, besides alcohol, nothing. It's affordable, and people do it. No denying it.
The effects marijuana has on the mind are considerable, but often exaggerated. Drugs don't deteriorate the mind in the essence they are shown.