It's not clear to me that this is so. If it were true, how do you explain Blogging, the Daily Kos, and even (here it comes) FreeRepublic.
We may not be emblematic of the public as a whole, but I find people who don't actively seek their News to be generally ignorant of current events & basic civics. Witness Jay Leno's "Jaywalking" segment.
Leno’s “Jaywalking” and other segments like it reflect how utterly ignorant many people are to the point they almost seem staged though I know they’re not but I see your point.