It's a mind altering substance, taken for that very reason, not just an offensive smell.
I just gave two examples whereas drug use does affect others. Drug driving puts others at risk and my children and I are being forcibly exposed to a controlled substance by virtue of our neighbours. It's antisocial.
Teenagers drinking aren't forcing it down someone else's throat. Smoking a drug and drinking are not comparable, although I also don't think teenagers should be drinking illegally anyway. There's published evidence of damage to cognition from weed smoking so teenagers smoking while brains are developing has deeper effects on both them as individuals and on society.
That's before you get into thinking about smoking being banned and proven harmful effects of it- I'll wager it's only a matter of time before similar stats are available for other smoked drugs such as weed for increased lung cancer risk and others, which again costs individuals, families and society. But the potentially impaired cognition of weed users would probably stop them figuring that out, or caring.
I guess you'll still find a way to trivialise any evidence that doesn't fit your prerogative though.
