I don't have a problem with marijuana being legalized.
The people who want to smoke it already do smoke it.
Legalizing it allows the government to tax it and regulate it as well as reduce the expense of locking up citizens for a low level drug offense.
It also would probably reduce dangerous elements for users who have to presently purchase it illegally from street dealers.
Lastly unlike cigarettes which are legal and kill approximately 400,000 people per year in the U.S. alone, marijuana has been sited as having medicinal purposes such as reducing nausea in cancer patients, reducing symptoms of bi-polar disorder, and it can help relieve/manage intra-ocular pressure in patients with glaucoma.
Having said that it will probably be a couple of generations before the vast majority of people let go of the stigma that was tied to marijuana during the "Reefer Madness" propaganda efforts to scare the public.
Gradually governments have started legalizing vices such as the policy/numbers racket became the lottery, loan sharking became "Payday loans", illegal gambling dwindled with the onset of legal casinos and boats, in some areas of the world prostitution is legal.
It was only a matter of time drugs would become a government revenue stream. Nevertheless "sin taxes" can't be counted on to sustain revenues. People have been known to give up vices!