I dont see where the two can be compared. Smoking is an action that directly affects those who have to breathe the air. My pistol in my locked car does not breathe or in any way affect ANYONE.
I dont smoke anymore but still do not agree with the smoking bans.
They're the same in that they are laws that take away the right of a business/property owner to choose what to allow on their property. Personally, I'd have to agree that anything in my locked vehicle in the lot is no business of anyone but me, but stoic private property rights defenders would dispute this.
I'm not sure how the law defines a locked vehicle as far as private property goes..