Robert Bidinotto has his take on Ron Paul and why his foreign policy view "is sufficient to completely disqualify him for any American public office, let alone for the role of commander in chief of the U.S. military."
Bidinotto frames his analysis in a unique and interesting way, comparing non-interventionist libertarians to those who are always making excuses--sociological, environmental, or otherwise--for domestic crime. He argues that at root both views share an attack on American culture and values because these are held to be the causal factors behind the terrorists and the criminal. It is our cultural 'imperialism' that causes the terrorists to attack us and it is our culture that causes the criminal to be a criminal. The analogy is a bit of a stretch, but I think it does provide some food for thought on parallels between libertarians like Paul and Rothbard before him and modern liberals.
(See my post on Ron Paul).