what Palmerston showed is that it is possible to be thrilled by and supportive of democratic movements in foreign lands, while remaining strictly uninvolved. Revolutions and rebellions are by their very nature unpredictable, fickle and confounding.This is to misunderstand Palmerston, who acted under constraints Obama doesn't share, first and foremost a very limited military capacity for intervention. The British navy could not intervene in Hungary, or Poland.
When there was a small or weak power to be manhandled in British interests, say Greece or China, Palmerston had no inhibitions about military action. (See "Don Pacifico" or "Opium Wars.")
Obama's intervention in Libya is more Palmerstonian than Sullivan allows. Qaddafi is a relatively weak dictator in a state readily accessible to European and American military force. And intervention, at least if the U.S. does not in fact put its own boots on the ground, is relatively cheap. Nor are there any great-power allies of Libya's whom Obama need fear to offend; this is an important difference between attacking Libya versus attacking Iran, or North Korea.
Palmerston is the poster boy for liberal interventionism; claiming his mantle in opposition to Obama's liberal intervention in Libya is odd indeed.