One very simple way I have of looking at this- if it makes you feel better, mentally or physically, and the positives outweigh the negatives, it's medicine!
Food is medicine. Eons ago was it the Greek Hypocrates who said "Let your food be thy medicine, and thy medicine be your food" in a format close to that at least.
I see what you're saying, and mostly agree. I think you have the right intentions & good thought, but in today's world, I don't think such a simplistic way of looking at it can cover the entire subject.
With controversial topics, even more so with weed because the medical use is such a big factor in national discussion/legalization, I think that "optics" are extremely important and always have to be considered.
Basically what I'm saying is, it's not doing the legalization process any good if we're looking like somebody on "My 600 lb life" scarfing down taco bell while simultaneously telling everybody that the Cheesy Gordida crunch in his hand is medicine.