He doesn't. He says so (unwittingly) in his interview with Marvin Kalb. See also Powerline on Mary Mapes. She says in her book that she'd never heard of FR, Powerline, or Little Green Footballs before they ruined her show.
Now that's shocking when it comes from leading journalists. It means they're completely unaware of the beliefs and views of a very large and powerful segment of the public. It means they're isolated, blind, and self-absorbed to an extent I never would have believed if they hadn't said so.
"It means they're isolated, blind, and self-absorbed to an extent I never would have believed if they hadn't said so."
That comes from living in Manhattan and only working with, reading about, watching tv shows about, and living near people who think exactly like you do. Running every thought through a party-platform filter and squashing any independent though helps too.