If pot has medicinal benefits, then it's okay to use it for those benefits.
A person has a right to do with their body as they choose, and the government shouldn't mandate what you can and cannot do with your own person.
Tobacco does have medicinal/health benefits. These benefits, of course, "have been determined to be far outweighed by the risks". (Unless, of course, they are able to help you.) Hell, nicotine has even been proven to reduce the risks of some type of breast cancer. (Betcha won't see that on the side of a pack of cigarettes... hey, why don't they print the bennies on the opposite (or same, for that matter) side as the warnings about the risks?)
So, I am doing something that may or may not benefit me, and may have ill effects, unless it doesn't, and may actually help me be more healthy (unless it doesn't). What I am doing will affect my body, and my body only, because I choose to only smoke outside, where any danger from second-hand smoke inhalation would be far below the amount of pollutants inhaled in a single breath of car exhaust on a choked highway.
Now I am doing something to my body that is my choice.
Where is the ACLU when I need them?