"Because of the potential to harm others?"
That's it in a nutshell. Society determines which are public goods and public bads, and activities that have shown a tendency to create public bads ought to be regulated. There can be no absolute which says that non-aggression alone absolves individuals of their responsibility to society, because unintended consequences are abundant, and if society can head off these unintended consequences before they occur, so much the better.
Absolute liberty (even keeping the non-aggression principle in place) does not lead to absolute happiness, and finding the balance between individual good and public good is an eternally ongoing process, but one that we should not shirk in the name of absolutes.
Monster Hunter: pissing me off since 2010.
