In the wake of the barrage from Larison, Massie and McArdle on the subject of the U.S. relationship to the IRA, I will concede that in spite of its official anti-terror posture, Washington treated the Irish Republican cause in ways that one cannot imagine the U.S. government treating the cause of Hamas. (And concede, as well, the limits of my knowledge of the ins-and-outs of the Northern Irish peace process.) But I think there's an oversimplication in Larison's explanation for why this might be so:
This comes back to the point I was making in an earlier assessment of the counterfactual. The IRA was a genuine terrorist group, but it was listed as such by our government most of all because it was a sworn enemy of one of our closest allies. The record seems clear: terrorist groups that are useful to us or harmful to states we officially oppose are given a pass, while those that target us or our allies are condemned in the strongest terms. That's the nature of things in the real world, I suppose, but it is something that none of the reponses to the counterfactual seems to be taking into account. Had things gone very differently in the last century and London and Washington became enemies once more, it is very easy to imagine that the IRA or similar groups would have been made into anti-British proxies of the U.S. government. In the unlikely counterfactual event that an independent Arab Palestine had emerged out of a very different '67 outcome, the official attitude towards the enemies of that state would have depended entirely on U.S.-Palestine relations. All of this is by way of saying that the official opprobrium heaped on Palestinian militants, for example, is primarily a matter of condemning the enemies of an allied state; their use of terrorist tactics is secondary to whether or not they are labeled this.
It's that "entirely" that I don't buy. Yes, pure realpolitik considerations enter into which terrorist organizations are labeled as such and which are not, and which groups the U.S. government works with and which it tries to marginalize. But so do other considerations - including not only ethnic, cultural and religious affinities (and the activity, yes, of domestic pressure groups), but moral considerations as well, and the extent to which the aims and deeds of a given insurrection can be read as being in consonance with American principles. Indeed, Daniel allows as much, later in the same post:
.... nationalist causes start out and end up with co-ethnics being their main sympathizers, and this forms the floor of their support, but when a nationalist cause is growing in strength and has appropriated the rhetoric of liberty (or democracy or some other favorable buzzword) its sympathizers will tend to come from many other groups who identify with the cause in a more abstract way. For that matter, think of the western European response to the Greek War for Independence-Philhellenes and political liberals supported the Greeks almost in spite of who they were, and rallied to the cause because of what they hoped the modern Greeks might become once they were free of the Porte. Obviously, Byron didn't die at Missolonghi because he felt strong ethnic ties to his comrades-in-arms, but because he was a romantic liberal.
Now the Larisonian worldview takes a highly jaundiced attitude toward "buzzwords" like liberty and democracy, and toward romantic liberalism in general, which is all fair enough. Certainly it's true that the American desire to make moral distinctions based on liberal ideals in foreign policy (or to dress up the requirements of realpolitik in idealistic rhetoric) often lends itself to willful self-deception. But even if you think this moralistic tendency is always and everywhere folly, it still has, I think, a great deal of explanatory power when it comes to how the United States regards a Hamas versus how we regarded the IRA: However brutal and extreme the Irish rebels were, it was far easier to see them through a romantic liberal lens, given their aims and ideology, than it is to hold a remotely similar view of the current leadership in Gaza.
Now it's clear that from our World War II and Cold War alliances that the American commitment to romantic liberalism can be compromised, and indeed that Americans can tolerate a high degree of barbarism among our allies, especially in the context of a perceived existential struggle. And to return, for what I swear is the final time, to Walt's original counterfactual, if the hypothetical Jewish Hamas were locked in a death struggle with, say, a terror-sponsoring, anti-American, theocratic occupier, there would undoubtedly be Americans arguing that we should be supporting the Jewish terrorists against the Arab terrorist state. But all things being equal - which is to say, if our hypothetical Palestinian republic bore at least a passing resemblance to the actual-existing Israeli republic, and the fate of the free world didn't seem to hinge on the outcome of the struggle - I have a very hard time to imagine Americans mustering much sympathy for a Jewish group with views, tactics and goals similar to Hamas. And indeed I think that American Jewish groups - the same groups that Stephen Walt holds largely responsible for America's anti-Palestinian bias in our non-counterfactual world - would, for the most part, be at great pains to distance themselves from their theocratic, terroristic co-religionists in the Gaza Strip.
But of course we'll never know.