"Seatbelt laws are immoral and unconstitutional because they are a pure example of government regulating behavior which does not hurt anyone but the actor."
Got to disagree with you on this one. I have witnessed very minor accidents where the driver was thrown from their position behind the wheel ( because of non-seatbelt use ) which then caused a total loss of control of their vehicle, thereby causing more accidents.
It is hard to drive your car from the passenger seat floorboard.
Even assuming that the "driverless car" problem causes a significant threat to public safety (and that is a big assumption in the absence of data), that is not the rationale behind the law. They were created to protect the safety of the person wearing the belt.