Indeed, the ideological opponents of liberals in America also have a smugness problem, but that may be because they themselves are also liberals.

"[T]he contemporary debate within modern political systems are almost exclusively between conservative liberals, liberal liberals, and radical liberals. There is little place in such political systems for the criticism of the system itself, that is, for putting liberalism in question" (Alasdair MacIntyre, Whose Justice? Which Rationality?, 394).

Smugness is a problem for liberal liberals and conservative liberals alike. Perhaps smugness is a natural temptation or outgrowth of liberalism itself.