The most powerful essay is Rieff's, who is one of the great liberal internationalist thinkers on the left of the foreign policy spectrum. Rieff is critical of Kagan's "binary" thinking, and he suggests Kagan dismisses too easily "the anti-interventionist, anti-millennarian tradition on liberal internationalism." But, for the most part, Rieff agrees with Kagan's argument on the essential neoconservatism of America's foreign policy tradition:
Doubtless, neoconservatism is only one modern iteration of America’s special mission to bring democracy to the world, at the point of a gun if necessary. But the liberal internationalist tradition is a distinct reality as well, and Kagan goes too far in trying to marginalize it in his otherwise useful and bracing piece....There's more at the link.
Having said that, it seems to me Kagan is absolutely right to insist that what we now call neoconservatism is “no aberration” within the American foreign policy tradition, and to mock the idea that, as he puts it, American imperialism was “some deviation from tradition foisted on an unsuspecting nation by clever ideologues”—the view that does indeed dominate the current thinking of liberals and the Democratic Party, which is awfully convenient given that it allows them to blame everything on the Bush administration, and somehow find it coherent to oppose the war in Iraq but back regime change in Khartoum in order to “save” the people of Darfur (regime change being the inevitable consequence, indeed a sine qua non, of any serious effort to intervene in that region, whether activists wish to admit this fact or not). Kagan is also correct, it seems to me, in pointing out how widespread support for the war in Iraq was among liberal Democrats and born-again realists when it still looked like things would go well and when the Bush administration was riding high. An argument about first principles between the American mainstream and the neoconservatives? Give me a break.
There is something absurdly smug and legalistic about the liberal view. Take, for example, the celebrated phrase widely attributed to Richard Holbrooke—our perennially self-anointed secretary of state in whatever Democratic administration that comes along—that the United Nations works best when there is “real” U.S. leadership. That may be literally true (though I think all it really means is that, structured as it is, the UN can do nothing serious that America opposes). But Holbrooke was almost certainly trying to make the larger point that the context of multilateralism, if respected by the U.S., both legitimated U.S. power and somehow transformed that power into the power of what we absurdly continue to call the “international community.” To this one could add the effort by the Princeton Project on National Security, led by Anne-Marie Slaughter and John Ikenberry, to wrap American hegemony in the sanitizing cloak of a concert of (world) democracies. No doubt the fifth-century B.C. Athenians, too, preferred the term Delian League, which after all was the correct name for the alliance of 150 city-states of which Athens was far and away the most powerful, to the Athenian empire. Empires claiming to be democracies always have this problem, and the U.S. is hardly the first empire to claim to be a democracy.
In short, if the distinction between liberal internationalists and so-called neoconservatives can be boiled down to the fact that liberals seek an America that is hegemonic, is the last best hope of mankind, is entitled to establish international rule sets (after consultation, to be sure), but one that acts, in Jefferson’s celebrated phrase, with “respect for the decent opinions of mankind” and emphasizes so-called soft power, while neoconservatives largely seek the same hegemony—but believe that because the U.S. is the last best hope on earth, has the most military power, and the will to use it, then when in doubt its views should prevail—frankly what we are looking at here is the perfect illustration of Freud’s “narcissism of small differences,” not two fundamentally different approaches to the conduct of American foreign policy.
I would just add that when Rieff - not to mention Kagan - suggests that liberal internationalists are closely aligned to neoconservatives in basic orientation, they automatically exclude from the analysis those on the far left of the spectrum, antiwar types who have argued against the Iraq war root and branch, and who have mercilessly criticized "liberal war hawks" for their initial support of the invasion.
This leftist antiwar school can be labelled "radical pacifism," and it might best be seen in Matthew Yglesias' recent writings on Iraq, and U.S. foreign policy more generally.
Yglesias is now considered a "foreign policy god" by Josh Marsall, and additional radical pacifists include, among others, Spencer Ackerman, TBogg, Digby, the Newshoggers crew, and to a lesser extent, Andrew Sullivan (a former neocon doing his best to get in on the good graces of the nihilist left).
The radical pacifists might claim the label "liberal internationalists" (that's Yglesias' game), but they are generally quite distinct from genuine institutionalists in their orientation toward the use of force, which - so far in my readings of these people - has yet to be considered a legitimate alternative in debates on current U.S. foreign policy (on cases like Iranian nukes or outside intervention in Burma).