I think that it's absurd that marijuana is illegal in the USA (or anywhere).
I highly suspect that much more harm is done to this country's citizens by alcohol and tobacco, yet they're legal. We waste too much money policing something that is no more harmful than these legal drugs.
In discussions about marijuana, I often come back to this memory from high school when I attended a rock concert. I'm pretty sure that it was R.E.M (not a fan, but my friends were - doesn't matter). You could pretty much split the lawn seats down the middle. One half was getting drunk while one half was getting stoned. As the concert went on, the drunk folks started to fight, threw things, created all sorts of mayhem. The other side was so peaceful and just sat there enjoying the music.
It was a very powerful moment. My friends and I had such a great view of this phenomenon as it progressed. The implications were lost on no one. I remember the discussions as we all wondered why the hell was alcohol the legal one.
There is no sensible explanation for making marijuana illegal, in my opinion.