Julian Sanchez has a judicious take on Rand Paul and on Libertarianism more generally:
At the scene of a four-century crime against humanitythe kidnap, torture, enslavement, and legal oppression of African-Americansideal theory fails. We libertarians, never burdened with an excess of governing power, have always had a utopian streak, a penchant for imagining what rich organic order would bubble up from the choices of free and equal citizens governed by a lean state enforcing a few simple rules. We tend to envision societies that, if not perfect, are at least consistently libertarian.
Unfortunately, history happened.
Rules for utopia can deal with individual crimesthe mugger and the killer and the vandalbut they stumble in the face of societywide injustice. They tell us the state shouldn't sanction the brutal enslavement or humiliating legal subordination of a people; they have less to say about what to do once we have. They tell us to respect the sanctity of the property rights that would arise as free people tamed the wilderness in John Locke's state of nature. They have less to say about the sanctity of property built on generations of slave sweat and blood.
Libertarians need to think harder about how our principles should degrade elegantly, how they can guide us through a fallen world where the live political options seldom afford a full escape from injustice.