To be honest, as someone who is unfortunately exposed to Fox News about 17 hours a day (it's all the mother in law watches) I can honestly say that of all the voices on Fox, O'Reily is the only one who even approaches reasonable. Something to keep in mind about the Fox network: These people aren't just super conservatives, they are crazy super conservatives. Fox and Friends and Glenn Beck are two shows that only somebody with bipolar going through a mania phase could really appreciate, and those are just two slices of the network. I mean, look at Tucker Carlson, their token Liberal. He wears a bowtie and says Fox News has no conservative bias, whatsoever. The only time he takes a liberal viewpoint is so that the people standing around him can make liberals sound unreasonable. This man is quite literally insane.
I think it's safe to say, where Beck has no comparison that isn't parody, O'Reily is the conservative Keith Olbermann or Chris Matthews.