There is definite logic behind the rather passive and uncritical position of certain libertarians on the problem in question. There are several aspects of the logic which, I believe, may help to explain their stance.

First, as you correctly observed, there is a gap between libertarian law and morality. In fact, libertarian law has nothing to do with the broader concept of morality; morality is deemed entirely a matter of individual subjective preference. The libertarian law is not derived from the analysis of moral and unmoral actions and choices (as it’s done in religions, social contract theories, and in Objectivism) but from the concepts of scarcity of goods and conflicting wants which in turn give rise to the need of the concept of property, the cornerstone of libertarian law. Hence the shocking disorientedness of libertarians when they are asked to evaluate issues that do not directly concern violations of property rights.

Second, they appear to have a peculiar picture of social reality: they tend to explain everything violent and evil in the world in terms of government failures, the government is the embodiment and ultimate perpetrator of evil. The common people if left alone will allegedly have all the “incentives” to SOMEHOW associate peacefully and trade and resolve interpersonal conflicts autonomously.

For these reasons I believe libertarian social theory is not in position to integrate important elements that determine social dynamics. Their passive position towards the threat coming from the ideology of violent Islam is a particularly relevant case in point.

…but not now, it seems. Not when even the very currency that we use is becoming a laughingstock.