You're making blanket statements that no longer hold true. What you get on the street certainly isn't safe because you have no idea what's in it, while getting it from a medical dispensary is a different proposition. They are actually held to standards in what they produce. And, like I said, smoking pot is so yesterday. Today's user can easily get THC in ways that impact no one else, even the busybody standing behind him. And also, like I've been saying, we humans have consumed these chemicals since the first guy noticed that drinking spoiled grape juice was fun, and THC, like all the other mood-altering drugs, is not very harmful at all in limited doses. It's not even addictive like caffeine is.
It is, moreover, therapeutic. It does reduce nausea, it does reduce pain, it does increase appetite, it does enhance sleep, it does treat glaucoma. You can deny all those you want to, but that doesn't make them untrue, it just makes you oblivious.