...a bit off-topic, but the actual problem is with the statement "smoking causes cancer." All you need to do is find one counterexample, and that statement is proven false (I'll even allow that it needs to be someone who dies of "old age," so we avoid cases of like 20 year old smokers dying in car crashes and such). You can make arguments that smoking is a risk factor for cancer, that smoking might exacerbate other conditions that contribute to cancer, but the causal link is dead, once you find a counterexample. I don't know of anyone who claims that smoking is "perfectly healthy." I know of plenty, though, myself included, that are skeptical of the claims that it's absolutely terrible. Is it at least a bit bad for you? Probably, but so are a lot of other things.