It looks obvious

The concept of public smoking bans, in my opinion, really gives you an insight into the psyche of a person. This is one of those issues that really separates those who believe in smaller-government-enforcing-their-own-biases from those who truly believe in smaller government and private property rights.

But I think there is more to this, and when Brad scratching the surface when he draws the line:

There is a dividing line between conservatives and libertarians, and this is one of the markers between the two. Non-smoking conservatives are usually quick to denounce smokers, and love the idea of smoking bans, because it stops people from engaging in behavior they disagree with. Non-smoking libertarians, on the other hand, may hate walking into smoke-filled bars, but understand that it is the decision of the bar owner to make. We dont always like the results of freedom, but to a libertarian, the alternative of oppression even well-meaning oppression is unacceptable.

The problem is, and smoke banning is only a symptom, that we get use to the notion that the government knows better. It is the notion that people are not to be trusted with decisions about their own life, and property. It is actually common to the conservatives and to the left. Both of these want to make for you the decision how to distribute your budget, who should you marry and what should you eat.
In my work I had to work with one of the state regulatory agencies and I discover that not only they do not have the best expert that protect the public interest but the most incompetent group of people that are being a burden on the development of technology and free market. The idea that any of these people knows what is better for me is ridiculous.
And I also question the ambition of the government to really ban smoking and cut a great source of tax revenue. But this is a subject to different post.