Why the argument? ??? Almost everyone knows how bad smoking is for you, and some people choose to do it anyways. Instead of yelling at them, or smacking them around it would probably be better to take them aside and talk to them if you feel like giving your input. I'm sure you'll find you'll get far better results.
The fact is, at 16, if you so choose to smoke, you may. It is illegal to buy them and to give them to minors, but if they "find some" then they can smoke them. This is part of our freedoms as Canadians. If I choose to smoke a cigar and you come and yell at me or "smack" me for it, then what would you expect me to do? "Sorry Sir, I'll stop this right away!" I don't think so. Some people think drinking is just as bad, and I choose to do it anyways. Does this make me stupid? I don't think so.
In my oppinion, and it is just that, I don't think that the violent approach is the right one, nor should you force an appology out of someone for their own oppinions. This is a discussion board and I think that people's oppinions should be respected even if not agreed with, no matter what the reason for disagreement (excluding racism, sexism and those sorts of things).
R.