Carr does not contest the claim that many journalists are biased in favor of liberals and liberal points of view; nor does he contest the idea that this bias can sometimes have an effect on political outcomes.... He could try to make the argument that it’s okay to slant the news on the theory that other people are slanting it in the opposite direction, but he doesn’t do that....
What Carr is saying is that there's news; what Ponnuru is saying is that there's politically inconvenient news, which, because it often (though not often enough) takes a lop-sided beating in the "liberal media," is fair game for re-slant, which is actually an original slant, since the initial presentation was merely "the news." Only inconvenient news requires spin.
Example. A news story: Mitt Romney's claim that yet more tax cuts would help to revive the economy is based on no credible, empirical evidence. Is this reporting slanted? No, because indeed there is no credible, empirical evidence showing otherwise. The reporting might well have "an effect on political outcomes," however, hence Ponnuru can declare the reporting itself to be political, thus legitimately exposing itself to political countermeasures of slant.
In other words, Ponnuru & Friends can't lose, since they've rigged the rules of dignified journalism. If a story is congenitally slanted to the right, it is conspicuously honest and therefore in no need of reinterpretation. If it's objectively damning to the right, however, it's still conspicuously political and thus by definition "biased"--a journalistic transgression that naturally cries out for balance.
In short, for Ponnuru & Conservative Friends there is no objective truth. This should be an immensely alien argument for traditional, "values"-prone conservatives to make; conservatives who have for years railed against the Relative Truthlessness of post-modernist philosophy. But it's not alien to them, because they are only political animals, not truth-seekers.