It's like if you're congratulating Steve Jobs on a successful iPad launch. You aren't obligated to also mention all of the products he has worked on that haven't done so well.
And I hardly doubt anyone was trying to convince you, or any other reader on HN, that Nate may have mispredicted something. In fact, I'm going to go out on a limb and say that there is no one on this planet who has not made a false prediction.
But since you're so adamant about this, could you put together a list of his complete record with links?
And sure, Krugman has a Nobel Prize, Clark Medal, Ivy League tenured job, nominated for a Pulitzer, but he'll have to live with spec calling him a partisan hack.
I'm not sure anyone would mind that tradeoff.