MondoBongo
Saintly
Firstly, you're going to have to explain how you're defining "privacy rights" to be able to distinguish between choosing to smoke and having an abortion. One is a true private decision by any definition of the word (smoking), while the other is a stretch (abortion). At best, the line by which you're using to differentiate the two is completely arbitrary. HIPAA has no bearing on the validity of an argument, and unless you're going to turn around and argue that the whole "my body, my choice" mantra thrown out by the left is only applicable to abortion, then you don't have much in the way of an argument here.
But all in all, it's irrelevant, since smoking is only half of the equation. The right to own a gun is a right EXPLICITLY protected by the Constitution, and there is simply no way for you to argue that it's Constitutionally permissible to tax a right specifically protected by the Constitution because it's "bad" while arguing that it's impermissible to tax a right not explicitly granted by the Constitution because it's "bad". None.
You're going to have to point me to relevant case law that states owning a gun is a private matter. Or that smoking is a private matter. I, on the other hand, will point you to Roe v Wade to demonstrate that abortion is a private matter per the courts.