The real problem here seems to be one of perception. Smokers (rightly) feel they should have somewhere to light up. Non-smokers (rightly) are unhappy with breathing carcinogens and smelling unpleasant (and they should know, they have a better sense of smell than smokers).

Saying "don't go into a pub if you don't like the smoke" is as unfair as saying "don't smoke in the pub". Who knows what the answer is. Probably ask if anyone minds and make sure your smoke doesn't waft into the faces of others.

Personally, I see smoking as a physical assault on a non-smoker. A smoker lights up in the full knowlege their smoke will harm the lungs and heart of non-smokers around, but they'll smoke anyway, and the rest be dammed. Not as direct as a kick in the nuts but even more harmful if taken regularly, and the intent is the same.

Mind you, I did smoke a cigar on Saturday night.