Matt and Trey do it again- they preach. And oh, how do they preach. They really do think they are the be-all end-all of edumacating us poor ignorant folk who don't buy into their philosophy of everything. The show has grown increasingly preaching and condescending, going so far as to putting their own personal views into the show, and using the South Park vehicle to present them.
Whatever stance you have as far as smoking goes (if you think it's dangerous or don't care), Matt and Trey completely ignore the fact that people have serious issues with smokers in public places. People who have allergies, respiratory problems, or even if people have a nauseous reaction to smoking (which is perfectly legitimate), should have the right to NOT breathe in that air. It is a public health hazard to at least SOME people, if not most (i.e. even if you don't think second hand smoking is deadly, it still disrupts the enjoyment of the space by other people).
In any case, that's MY view on it. However, Matt and Trey don't open anything to debate. They make Rob Reiner look like a power hungry monster (the most random person possible, since there really aren't many famous people so adamantly against smoking they had to make a scapegoat)