Many people have a hard time accepting that, when it comes to politics, as in the rest of our practical lives, "we see now through a glass darkly." They wish for a "politics of perfection" (or "politics as the crow flies") that is simply not available in this world.
For instance, David Gornoski suggests that, in politics, we should not "settle for hiring any person to represent you who leaves even one nonviolent person confined in a cell you yourself wouldn’t place there." With only a little extrapolation, we can see that this implies, "No one should accept any legal regime in which they disagree with so much as a single decision made by the legal authorities."
But in a fallen world, no such legal regime is possible. Our choice is not between an imperfect legal regime and a perfect legal regime, but between an imperfect legal regime and no legal regime. Eric Voegelin lays out the reasons why:
"The first of these reasons is the just-discussed calculus of error. Since there is a discrepancy between true order and empirical order, enforcement is necessary in order to eliminate disobedience on the part of citizens contending that the content of the rule is not in accord with the Ought in the ontological sense.
"The debate about the justice of the law must remain within the forms of political criticism and political action through voting. If the existence of the society is to be preserved, the debate cannot be permitted to degenerate into individual decision and resistance.
The acolytes of the politics of perfection abhor this unavoidable arbitrariness in any actual legal regime, and thus dream of a world where all complexity has been banished. We could hardly find a clearer expression of this politics of perfection than in this essay by Murray Rothbard, where he argues: "In short, there exists another alternative for law in society, an alternative not only to administrative decree or statutory legislation, but even to judge-made law. That alternative is the libertarian law, based on the criterion that violence may only be used against those who initiate violence, and based therefore on the inviolability of the person and property of every individual from 'invasion' by violence."
We should just set ourselves thinking, and come up with the perfect legal code, "before enshrining it as a permanently fixed libertarian code or constitution." We will ignore the issue of how, with no central legal authority, we "enshrine permanently" any code or constitution!
Of much more central importance is the wildly loose use made of the concept of "violence" in this sort of scheme of perfectionism. Of course, almost every legal regime that has ever existed has outlawed simply walking down the street and koshing the next person you meet on the head. So in that sense, just about everyone is against "violence."
But the simple, straightforward definition of "violence" we use in everyday life certainly will not get us an anarcho-capitalist legal regime. For instance, if I lie down to sunbathe in a meadow that happens to be owned by Walter Block, he would contend that he has a perfect right to shoot me for doing so. In the ordinary usage of the word "violence," I did nothing violent, while he did. In order to get around this little problem, he re-defines my lying down in an open meadow as a "violent" act, and his shooting me as "self-defense."
Since even followers of Rothbard have their own preferences for what should be outlawed, we find that even amongst themselves they can't agree on what is "violent." Murray Rothbard likes the idea of copyright, and so he defines copying a work without permission as "violent." But Stephan Kinsella doesn't like copyrights, so he defines enforcing a copyright as "violent."
Walter Bloch likes the idea of open borders, so he defines restrictions on immigration as "violent." Hans-Hermann Hoppe doesn't like open borders, so he defines open borders as "violent."
Opponents of fractional reserve banking thinking FRB is violent. (It is "fraud," which anarcho-capitalists, to squeeze it into Rothbard's legal straightjacket, have had to call "a form of violence.") But proponents will, of course, find an effort to ban FRB to be a form of violence.
So, in order to get their preferred legal regime out of Rothbard's dictum, anarcho-capitalists have to redefine the word "violence" to mean... well, basically, they redefine it to mean "things I think should be illegal." And "non-violent" means "things I think should be legal." (Essentially the same magic trick goes on with similar attempts to conjure all valid law out of a single principle, e.g., advocates of "Anything that's peaceful" just define things they want to be illegal as "not peaceful.")
Rothbard suggests that if we just think clearly, we can come up with an unambiguously just legal regime, and, even with no central enforcer, it will be so blindingly obvious to everyone that it is correct that it will be "permanently enshrined" as an eternal constitution. And yet, even among the .1% of the population that are anarcho-capitalists, there are dozens and dozens of different ideas as to what this eternal constitution should contain. So although this tenth of a percent of the population who basically accepts Rothbard's idea can't reach any agreement amongst themselves as to what exactly it entails, they believe that getting the other 99.9% of us who think Rothbard is blowing hot air to overwhelmingly accept their personal version of Rothbardianism is a real possibility.