For forever and a day, the concern about marijuana has always been the idea that it leads to more serious drug use. A counter-argument points out that alcohol is legal and more apt to cause someone to cause damage to self and/or others, while marijuana only makes people hungry. I have heard these arguments for a long time.
Interestingly, legalizing it would knock pot dealers on their butts if people could get it legally. Personally, I would be more concerned about hard drugs that destroy people's brains and their lives. Addiction is a terrible thing. And I am not certain if it's true that marijuana leads to the use of harder drugs.
Who is to say it will always be illegal? Prilosec and Allegra (for instance) used to be available only with a prescription; now they are available over the counter. Perhaps the benefits of legalizing marijuana have not yet been exposed. In time, things may change. However, putting any kind of drug (even cough syrups with codeine, years ago) in the hands of the young can have long-reaching effects. It is unfortunate the marijuana seems such a concern in the hands of young people when violence on the streets, and a string of abusive behaviors are visited upon our young everyday. The world is not a safe place for kids. However, if the government controls the substance to protect kids, I'll support that. If it is necessary to improve the quality of life for sick people, I'm for that. Having witnessed an older friend die of bone cancer recently, I thank God for prescription drugs like morphine which are made available to those who need them.
Give it time. Further research may be needed, and then the government and doctors may see it in a different light.