Why does Fox News have such a terrible reputation?

I've watched it countless times and would agree that it is right-leaning. However, networks like CNN and MSNBC have just as strong left-bias and I have watched both of these countless times as well, yet there is a lot less talk of these biases. People like Bill O'Reilly, Glenn Beck, Sean Hannity, and Rush Limbaugh (not on Fox News but a conservative political commentator) are so antagonized by the public, yet I can't think of a single liberal who has this type of reputation. Is it because there are no significant liberal commentators? I def don't consider Keith Olbermann to be significant. Most people don't even know who he is.