Well, here is my 2 psi...
I'd smoked for 25 years. Medium to heavy smoker most of my adult life. Had tried to quit many times unsuccessfully. Few years ago picked up SCUBA. Right away figured that air quality is important to divers and NEVER (let me repeat-never) smoked on dive boat on day trips or around other divers, had to wait till I would get near my car to have that stupid smoke or two. Yeah, it was tough at times. But I considered this a common sense.
Guess what: I quit. Guess what: I've lost about 25 Lb since I quit. Forget that quitting is difficult, forget that quitting makes you gain weight. It's an urban myth. In my case it took a 2 hour video ("Easy way to stop smoking" by Allen Carr) to straighten my brain (took longer lunch on Jan. 5 2012, watched the video and never made a single puff since, don't want to as well). Oh, an no, the video (or the book by Allen Carr) doesn't try to scare you in any way.
Quitting doesn't make you gain weight. Burning less calories then calorie intake makes you gain weight. Simple math. You want to eat more and not gain more weight-exercise more.
Anyway, back to the original topic: I don't like "smoke nazi", even now, after quitting. These are the people that will come close to smoker on purpose and will advertise that smoking is bad for you by coughing, etc., will throw loud fits about how smoke 2 miles away bothers them, etc. But I do think it's a very reasonable for people to expect not to breath in cigaret smoke on dive boat. Some people have their sinuses and even bronchi irritated by smoke (including my son) which doesn't exactly help enjoying day of diving. If you smoke-don't smoke on dive boat, please. Yes, you can do it. Believe me. You will not die, I promise. If you have to, use nicotine replacement (e-cigs, Nicorette, anything). If you still have to, make sure you do it somewhere where it cannot bother anyone. But most boats are too small to avoid getting some smoke to people. So, it's best to completely avoid it.