No one smokes 10-20 marijuana cigarettes a day like the 1-2 pack a day cigarette smokers who damage their lungs and get cancer.
Marijuana ought to be legalized and sold in a controlled fashion like alchohol. It is, on the whole, probably less dangerous than alchohol. I've never heard of a person DYING from using marijuana; it must be pretty rare (more than 100,000 people a year die from alchohol related diseases and accidents). It doesn't even increase their auto accident rate (they just slow down).
I don't use marijuana. But I don't like the enormous criminality and corruption that follows from its being illegal. It's just like what happened during Prohibition. The corruption and crime are worse than anything the drug does.
I think the real reason they don't want it legal is their inability to tax it.
If it were legal, you could just grow your own.
If you had to buy it, how could they regulate the underground enough to collect "their share" from it?
Right now, they collect more cash from drug busts than they could with a sales tax.