I had a very close friend at an outdoor party one night decide to try marijuana, he ended up jumping off a bridge thinking he could "fly".
May I suggest that perhaps it wasn't the marijuana that caused your friend to jump off the bridge, but perhaps a mental illness (perhaps bipolar) that caused him both to A. DECIDE to try marijuana, and then B. jump off the bridge. Bipolar in the manic phase reveals itself at times with much lowered inhibition thresholds -- it can lead to over spending, gambling, driving too fast, drinking binges, drug binges, (posting things that should probably not have been posted,
speaking of myself, of course), lipping off to supervisors, etc. What I'm saying is that if the plant, marijuana, had never existed, your friend might have STILL jumped off that bridge. To assume it was the pot that caused it, is a false assumption.
I had another good friend who smoked that crap and moved up to cocaine because "the buzz" he got off Marijuana just wasn't good enough.
There ya go! It's not that the marijuana made your friend graduate to cocaine -- it was the fact that he had an addictive personality (or was bipolar, too) and WANTED a better buzz! Marijuana didn't cause the desire for a better buzz--marijuana was just a thing he tried in his pursuit of finding the better buzz.
I have another good friend who smoked Marijuana once and is now crippled for life after thinking they were a race car driver and crashing.
Classic bipolar behavior.
Now, should we, as a society, outlaw all substances because SOME people have a bad reaction to them? Should we demonize all substances that certain individuals have an intolerance to? Sugar causes diabetics great harm...should we ban it and jail people who use it? There's no question that substances of abuse are a problem to people with mental illness--but should those without a mental illness be denied the freedom to functionally consume those substances because a certain population in society has a problem with it?
At issue here is freedom! I KNOW you don't believe in a Nanny State, but at the heart of this issue, is the government telling you what you can or cannot do in the privacy of your own home, not for YOUR greater good, but because your neighbor has a disability toward that substance. That is NOT what our founding fathers had in mind when they set up our government in this country.