Terry McDermott takes a look at Fox News and notes the obvious: they don't tend to have a lot of Democratic guests:
This appears to be politically motivated, but that could be just an artifact — the content seems political but the primary aim is much more likely commercial. Cable news is not literally a broadcast business, but a narrowcast. At any given moment, there are a relative handful of people (in peak hours less than five million and in non-prime hours half that, out of the U.S. population of 320 million) watching all of these networks combined. American Idol, in contrast, routinely draws 30 million. Although cable news is a comparatively small market, it is a small market with a much larger mindshare, mainly because the media are self-reflective, creating a kind of virtual echo chamber.
....[Roger] Ailes’s most valuable insight was that sharp opinions do not necessarily chase an audience away. In fact, they seem to have created one. There is no worry of offending a broad audience, because there is no broad audience to start with anymore.
I think McDermott's suggestion that this might not be politically motivated is a little silly, something that he pretty much concedes in the rest of his piece. Still, the main point of this paragraph can hardly be emphasized enough: hardly anyone watches cable news. Even in prime time, Fox has a couple million viewers — that's about 1% of American adults — and the other operations have a million or so. Cable news is a molehill that gets routinely turned into a mountain range because they happen to be talking about the most self-obsessed bunch of gossip hounds in the country: politicians.
But the reality is that almost no one is watching. Take away the echo chamber and Glenn Beck would be about as important as a guy on a soapbox in Central Park. Which is basically what he is.