If you are smoking cannabis then you risk lung cancer, amongst other cardio and pulmonary disorders, because of the higher tar and hydrocarbons in cannabis.
I think you are seeing a conspiracy, where there isn't one.
Cannabis whither you want to believe or not 'IS A DRUG' -- so get a grip of reality.
Making it legal, does not in the end make it right to take drugs.
Drugs change your reality -- they don't make it better -- they make it different.
And long term use can result in a psychological addiction to say the least. And a retardation of the serotonin usage by the brain, and it's manufacture by the stomach.
The brain after cannabis euphoria, suffers a down -- a deppression -- like a hang over.
One can not get off one drug by using another. That is an addicts logic to conclude that cannabis can help with opioid addiction...likened to drinking whiskey to get of cigarettes, n'est ce pas.
You will find numerous studies which show that pot smoking in fact REDUCES risk of lungs cancer compared to no smoking people (ie people who smoke neither pot nor tobacco).
But I agree with you that teens shouldn't smoke too much to avoid being turned into life-long brain damaged slow motion zombies.