The non-aggression principle, or NAP as I'll be referring to it henceforth, isn't something that a group of wise philosophers came up with. It is something written on our souls, something that has a place in the tenets of every major religion on earth. It is nothing short of the Golden Rule itself: do unto others as you would have them do unto you. Don't hurt people. Don't steal. Don't be a bully; talk things out, and do your best to persuade others using only words, not coercion and threats. Our parents taught this to us, as their parents taught it to them. It is the only way to truly treat others as equals. When you encroach on someone's person, whether it be with physical violence or theft or even angry words, you are, in essence, saying "I matter more than you do. My needs outweigh your needs."
We all expect this of ourselves and of one another, even though we all fail to put it perfectly into practice. The NAP is the standard to which a moral person and a moral society is held. Yet beyond our private lives, we live under a system completely based on the use of aggression. What is wrong for an individual has been made legitimate for the State. The State hurts people. The State kills people. The State steals from people. The State kidnaps people. The State enslaves people. The State is a bully. The State is coercion, force, aggression, and domination. To the State, you are not significant. Every time a new law is passed that violates even one person's natural rights, the State is saying "We matter more than you do. Our needs outweigh your needs."
Every time you pay a tax, you are being robbed. If you resist, the "at gunpoint" part becomes real. Every 18 year old boy who is forced to register for the Selective Service risks possible enslavement and even injury or death in the event the State decides to resume conscription. Failing to do so leads to more kidnapping and theft, in the form of a $250,000 fine or 5 years in cage. Behind every law, just or unjust, is a loaded gun. Behind those loaded guns are officers of the State "just following orders."
The only legitimate role of government is to protect the rights and liberties of individuals. Beyond that, however, it represents an illegitimate use of force. Remember: if it's wrong for you to do, it's also wrong for the State to do.