You don't think Bill O'Reilly and the rest of the far right don't know what they're doing? Bill O'Reilly isn't stupid. He's a liar. With him, and others like him, you have to realize that the words they say tend to mean the opposite of their dictionary definitions. It's like those ministries in the novel Ninteen Eighty-Four. It's exactly that.
I suspect that this has to do with that famous quote which I think is attributed to Lenin, about how a lie told often enough becomes a truth. If you repeat often enough that the media is going too far with its liberal bias, people are going to assume that the media has a liberal bias. It's a foregone conclusion at that point. It sounds stupid to people who know better, but I'm not sure everyone sees it that way. I mean, Fox News viewership is a pretty good indication that Lenin was right.