"I am armed and you are armed and we are armed together
And we will watch each other through calm and wild weather -- "
Sometime around eighth grade I became more political and philosophical, and discovered the Libertarian Party. From them I got the Non-Coercion Principle: "I swear not to initiate force or fraud against another." The rigorous application of logic -- an activity I am well suited for in such things -- to this principle easily produces the entire LP platform as well as my childhood beliefs. Very nice and straightforward, but something about it bothered me. It smacked entirely of Enlightenment natural law, which was appealing, but in imagining verbally confronting a human predator I couldn't see how one could make any headway, which seemed rather pathetic for a law. A few years later due to a couple of essays on the extropians list I realized that my misgivings were right -- the NCP was an assumed axiom and it did not make sense to argue to a Nazi that they were violating it and initiating force. They wouldn't care and there was no way of making them care other than threatening to shoot them.
So for a while I thought about taking the NCP as my personal axiom, but I hesitated to take such a direct step. Not that my actual ethics or behavior changed through any of this; I am describing a distinctly philosophical activity of trying to justify as logically as possible a given behavior, which might be changed if I came up with a good reason to do so, but otherwise could be takes as functional and intelligent. So I drifted for a while, although I did learn of the Prisoner's Dilemma and TIT for TAT, the simple and generally most successful program of "cooperate initially, then do whatever she did last". It can be regarded as essentially libertarian in spirit -- be nice but fight back -- and learning that it was most successful (but not always -- it depends on the setup and the environment of competing programs) was rather heartening.
A brief investigation into Objectivism and its attempt (failed from my point of view) to derive ethics from first principles about one could know and observe without question crystallized the next step, which was partly to realize that not only does Might make Right, but everyone except the European Enlightenment has realized this. Even Judeo-Christians. Rather, especially Judeo-Christians; why else the threats that "God Almighty" will send you to Hell if you disobey. The Almighty defines Right. Not necessarily in a moral sense -- one is free, nay, encouraged by me to disagree with whatever the God proposes (or might be proposing if It existed) but as practical matter Might gets to call the shots, unless those Might tries to boss are truly willing to die for their beliefs. If what Might wants is their death then their opinion hardly matters.
The other part of the step came from considering both TIT for TAT and social predators in nature, especially when prompted by debates about gun control. Animals like wolves have various forms of ritual combat and rules of engagement, such as don't rip out a proffered throat. The fact that these are probably genetic rules is irrelevant to the point behind them, which is that entities which are heavily armed want to avoid full confrontations between themselves precisely because they are so likely to kill each other. Bullies aren't that dumb: you do want to limit casual predation to the weak. If you face someone who can fight back you want to be sure you care enough about what you're trying to steal to risk injury. Given that most of the time someone will care more about keeping their own life than someone else will care about taking it I would expect a fairly libertarian order to spring up spontaneously.
But I've drifted, haven't I? Well, no. The justification of my own ethics has gone back to what it was originally -- I want to be left alone simply because that is my nature, and I leave others alone because I don't want to get hurt. By empathetically assuming that others also want to be left alone, and cautiously assuming that they are as well armed as I am, I concoct a libertarian order. Human reality is rather different, which I try to explain by noting that most people are not equally armed, and also that energetic young people in particular, but many people in general, assume "it can't happen to them." Idealistically I hope that if people were decently able to defend themselves and had a good grasp of risk assessment that a polite and free society would arise naturally, because no one could get away with being bossy.
One clarification -- the predatory etiquette justification gives no reason not to prey on the weak and helpless, those who cannot or will not defend themselves. Truth to tell, I have no logical reason why I should not. But I feel I will not. Perhaps I should say I have another axiom: "be nice anyway if you can." (Actually, that is pure TIT for TAT behavior.) Perhaps memetic evolution has incorporated a logic deeper than I can reconstruct by the age of twenty. Perhaps I am silly.