Believe it or not, most doctors have absolutely no expertise on marijuana. It's not studied in their training. But if you look at the actual research, there are no medical problems associated with marijuana consumption except that it may affect people who have existing psychosis, and they, like most people can buy it easily on the streets. 
Also, no one is claiming that it's good for our youth. But they can now get it more easily than alcohol in most cities. 
Stop with the fear-mongering.