They are by their very nature situational and subjective. No honest man operates by "sheer utilitarianism" (Which, by the way is also subjective, who decides what is useful?). We all have emotional or cultural standards by which we base our actions, and then we sometimes are forced to modify them by necessity, or maybe just to do what some other principle, like our sense of justice, says is right. Even "thou shalt not kill" has many allowable exceptions.

But it is my experience that honest people may have different principles from my own, and I need not alienate them by implying they don't have any because their principles do not coincide with mine. And I certainly can't expect a third party to accept my program over another's simply because I say they don't have any.

Philosophy and politics are not physics or mathematics; you simply can't declare a handful of philosophical axioms and then start proving theorems based on them. And principles vary over time, over history, and over individuals as well. Your opinions about libertarianism and free markets may be worthwhile, in part over even in whole, but they don't derive from the laws of nature. They are just your opinion.