I think George Packer does his readers a disservice by trying to construct a parallel between conservative reaction to Scott Beauchamp and liberal reaction to O'Hanlon/Pollack:
The same people who believed the first story refused to believe the second, and vice versa. In a sense, they believed or refused to believe each story before it was published—even before it had occurred. What mattered was whether the story supported or undermined their view of the war. This kind of thing depresses me even more than the thought of Bradley Fighting Vehicles running over stray dogs.
But that's not what happened. I haven't seen people question the veracity of specific anecdotes Pollack and O'Hanlon offer. In fact, it would be absurd to do so. If they say they spoke to soldiers whose morale was high, no doubt that's because they did, in fact, speak to soldiers whose morale was high. What I, and others, have done is question the strategic judgment they offered about the surge. We suggested, moreover, that their upbeat analysis of the situation should be put in the larger context of them both having extensive records of poor judgment on Iraq, with errors invariably coming from being too hawkish.
The right, meanwhile, not only insisted without evidence that Beauchamp was lying, but suggested that the publication of his story was motivated by The New Republic's desire to undermine the war even though TNR has never opposed the war and doesn't oppose it today.
UPDATE: By the same token, I should say that the whole thing is apples and oranges. If you agree with the main point of the Pollack/O'Hanlon op-ed, there's an obvious policy upshot: the surge should be continued for months and talk of withdrawal should be stopped. The Beauchamp article, meanwhile, no matter how true or false it may be, has no implications whatsoever. "This dude killed some dogs, therefore we should leave Iraq" would be an absurd argument.