It doesn't make economic sense that CNN would respond to the runaway success of Fox News by moving to the left, as Posner claims. In every other industry, competitors follow trends; they don't run from them. When a reduced-calorie snack food is introduced and becomes a hit, that doesn't "push" the other snack food companies to roll out their own "extra-calorie!" versions.
I enjoy making fun of CNN as much as the next guy, but CNN is not that liberal. It may be liberal compared to an average American, but it's certainly not liberal compared to CNN pre-Fox News. Consider that Peter Arnett used to be treated as a serious journalist on CNN. Even his work on the "Tailwind" hoax program did not jeopardize his standing.
Now, even MSNBC won't hire him. (Although I hear Arnett has a big interview at al-Jazeera next week – good luck, Peter!) After initially trying to stand by him, NBC was forced to fire Arnett after Americans erupted in fury at his traitorous comments on Saddam's state-run TV at the outset of the Iraq war. This is what liberals mean when they say the country has become "polarized." Now when they try to put traitors on air, Americans complain.
Indeed, the only network still assiduously following Posner's "give the consumers what they don't want" business model is MSNBC. They will go to dead air before giving a conservative his own TV show (except poor, lonely Joe Scarborough, who has a terrific show – if only anyone knew how to find MSNBC on the dial!).
Turning on TV and seeing Wolf Blitzer instead of Peter Arnett is not evidence of the media becoming more polarized. It's evidence of the media becoming more sane.
Instead of recycling tidbits he picked up from books written by people who subscribe to the bizarre notion that the media has a conservative bias, Posner should occasionally consume some media himself. It's a wondrous example of the virtue of competition. The country isn't more divided. All that has happened is that, now, conservatives are talking, too.