Smoking is a dirty, disgusting habit. Besides increasing the risk of heart disease and lung cancer, it causes corneal ulcers and is directly implicated in macular degeneration which causes blindness. It's also an environmental disaster, with all those filters that may not be biodegradable and growing tobacco plants which serve no function but to rob nutrients from the earth, as well as increasing air pollution.
And besides all that, people who smoke often have foul breath and therefore it is an affront to society. In addition second hand smoke is just as deadly as primary, so people who smoke are nothing less than completely selfish humans who could give a rats ass about others around them. This is unlike other addictions like heroin which, if it were legal, all a person needs to do is maintain dosage and no other member of society is affected.