I'm "totally" not. It only takes three joints a day to do the same damage to your lungs as 20 cigarettes. What will become of pack-a-day smokers who transition from tobacco to marijuana when the latter is commercially available? The act of getting high is what compels people who use marijuana to do so. The "medical marijuana" strawman has been discredited. And, as for your last appeal, you say that is if people don't have the option to abstain completely from all of it.
None of this is convincing at all unless you cite your sources.
Here's a good summary of the effects of marijuana on respiratory health. It's not good, but there's no clear 3:20 ratio of damage like you're claiming:
http://adai.uw.edu/marijuana/factsheets/respiratoryeffects.htmMedical marijuana is of course a real thing, here's a summary of its efficacy on neurological disorders, particularly MS:
https://www.aan.com/Guidelines/home/GetGuidelineContent/651Marijuana as a gateway drug is also not well established:
http://www.rand.org/pubs/research_briefs/RB6010/index1.html