The Motte and Bailey of Libertarianism
I identify as a libertarian. At times I have been at least partially guilty of the misstep I hope to illustrate below. I’m presenting it here in the hope that by clearly identifying it, it’s easier to avoid it and to improve our rhetoric.
In this case I think the problem has to do with overselling libertarianism with attractive anti-violence/anti-aggression catchphrases. There is some truth to these, but at the same time I don’t think they hold up well to scrutiny.
Here’s Scott Alexander’s explanation of what a motte-and-bailey doctrine is:
the motte-and-bailey doctrine is when you make a bold, controversial statement. Then when somebody challenges you, you claim you were just making an obvious, uncontroversial statement, so you are clearly right and they are silly for challenging you. Then when the argument is over you go back to making the bold, controversial statement.

Libertarian: Libertarianism means not using threats of violence against peaceful people. [Bailey]
Challenger: But someone in breach of contract might still be peaceful, yet you believe that threats of violence against them might be legitimate. And you believe threats of violence against a trespasser might be okay too, even though they are non-violent.
Libertarian: I mean peaceful in the sense of not violating anyone else’s property rights. By property rights I mean neo-Lockean property rights. I think a determination of whether rights have been violated or not is best arrived at through the operation of a polycentric legal system. Rulings in individual cases are best made in reference to the case law that emerges in this system. If you have the time I could explain why I believe this system would be better than the status quo in all the ways that matter. [Motte]
[Challenger makes talk-to-the-hand sign and leaves.]
Libertarian (softly): Libertarianism means not using threats of violence against peaceful people. [Bailey]
I talked critically about the non aggression principle in a similar vein here.
