Adam Serwer points out, correctly, that liberal excuses for extrajudicial killing make their opposition to torture nonsensical.
The question, though, is whether there is anything more consistent in Serwer's limited-but-appropriately-ruthless preferences for warmaking. Last year, after bin Laden's killing, he and I argued about the moral status of pacifism, which he equated with that of barbarism, and what the proper amount of bloodlust should be in the liberal imagination. The post-OBL killing period was notable for me in part because of the typical redbaiting and eliminationism that always come when mainstream liberals get annoyed with genuine antiwar sentiment. In the larger perspective, it was just a fascinating time to observe the liberal mind.
The contemporary liberal's foreign policy rests on a tenuous negotiation between principled nonviolence and the need to express sufficiently militarist attitudes to remain politically palatable. This negotiation causes liberals to out-Herod Herod, to dress in the ill-fitting uniform of belligerence, based, I suppose, on the notion that this performance is necessary to win elections. That's folly; you can't out war the GOP. But they try, and they hope to both build a generally restrained military apparatus and simultaneously lionize military efforts they deem worthy.
Serwer believes that you can have both; he thinks that you can kill the bad man and bust out that creepy red white and blue Spiderman suit and party in front of the White House, but also have a foreign policy that isn't aggressive, militaristic, or reckless. And I'm suggesting: no, perhaps you can't have both. Following the death of bin Laden, celebrating liberals assured us that this would be the pretext for ending the war on terror and restraining our military machine. Instead, we have launched more undeclared wars, dramatically expanding the breadth of a program that kills innocent people without accountability or review. We have not slowed the pace of our assault on the Muslim world; we've quickened it. The question that he should ask himself is whether there isn't some connection between so many Good Progressives dancing in the streets because of killing and their tendency to take killing less seriously.
Serwer talks about an "obvious legal and moral bright line" in his post, and this sort of terminology is found throughout his writing on foreign policy. The problem is that politics occurs in the hearts and minds of human beings, and bright lines have a habit of bleeding together within them. People who are told by both sides that it's okay to celebrate killing and war are not going to apply the nuance and discrimination that you might want when the next war rolls around.
Now, it happens that I too believe in obvious moral bright lines, and as part of a fallen species I could never say that I can maintain mine. And yet I find that they have a simplicity that makes it far easier for me to police them. Don't kill. Do everything possible to avoid war. Never suppose that killing is necessary. Never suppose that such a necessity could excuse such killing. Don't imagine that any killing could ever be simplistically justified. Never celebrate death, under any circumstances. These rules are very difficult to live by, but no more so than Serwer's, and unlike with his it is very easy to know when they have been violated.
Not having any influence, I doubt that good antiwar liberals-- and they are good, and generally antiwar, make no mistake-- I doubt that they'll listen to me. But I suspect that they will continue to be confronted with the question of whether you can oppose war most of the time and lend it uncomplicated moral support sometimes. They'll be so confronted because they too frequently contribute to the justification of a murderous military apparatus that never needed much justification anyway, and then shudder under the consequences. There will be more bad wars, wars they don't like, that they'll fail to prevent. They'll go on losing and maybe someday that losing will force them to consider whether war is a beast you can feed only when you want to.