So replace dementia with mind numbed stoning?
According to that logic, we shouldn't be using opiates as medically prescribed pain killers either, because they numb the mind (more so than THC, and much more addictive). I never understood the mindset of people who defend the medical (and even recreational) use of some classes of drugs while getting hysterical over others.
I used to be a heavy toker, and do admit that there are downside effects; most especially, an overall "slacker" type attitude towards life, and an avoidance of conflict to the point of ineffectiveness. Again, that is with heavy use. Although I was a heavy user and immersed in the culture, I would get in arguments with my cohorts who believed that it was natural and healthy, and touted its cure-all properties. Knowing that there are vaporized and pharmocological methods of delivery, there is no way that smoking pot can be considered healthy. Introducing any kind of carbon based smoke into one's lungs on a daily basis, via joint, pipe, or bong, is never healthy. My suspicion is that non-smoking lung cancer sufferers didn't get it from "second-hand smoke", but through constant pot smoking.