The smoker has a right to, as you put it, “poison himself.” Your right as a nonsmoker is to either stand elsewhere or politely ask the smoker to do so.
It seems the nanny state has done the same thing to common courtesy that it has done to common sense.
It’s my right to stand exactly where I’m standing and tell the smoker to get his poisonous smoke out of my proximity. That smoker has exactly ZERO RIGHTS to have his poisonous fumes around me.