Are you gonna let your kids smoke?

My parents let me smoke, but I wouldn't let my children smoke anymore than I would "allow" them to drink alcohol underage.
If they are young and healthy, then there would be no reason for them to use it medically; if they are young enough for me to dictate what they "can"/"can't" do, then I assume their brain will still be undergoing development and I would not want to risk impeding that short, precious process of neurological revolution. Furthermore, a child does not have a fully developed frontal cortex, which means they are literally UNEQUIPPED to be making decisions.
Hell, most adults do not make wise decisions and they often lack the foresight or possess the thinking abilities to choose the healthy, right path.
I don't see it as anymore harmful than alcohol, under most circumstances.
But no - as an adult parent, I would not allow my child offspring to engage in recreational (or medical, if I can avoid that) drug use.