I don't see how driving being a privilege and not a right has anything to do with seat belts.
As usual, you're not very smart.
If something is a right, then there is no way for the government to attach preconditions to exercising that right. Hence your argument of "you can't tell me what to do!" might hold water. For example, the government can't tell you how or when to exercise your religion, because free exercise of religion is a right, not a privilege.
If something is a privilege then generally the government is granting you a special permit (in this case, a permit to operate a motor vehicle on public property) in return for you agreeing to certain conditions (in this case, obeying traffic laws). So when you got in your car and drove on public property, you are agreeing to wear your seatbelt.
If you were ticketed on private property, it is probably the case that the owner of the private property has an agreement with local government that in return for them policing his roads, he has granted them jurisdiction to enforce normal traffic rules on those roads.
If you really want to do things your own way, stop using property that is not explicitly yours. Have fun, Thoreau.