If Bush or a prominent Republican were credibly accused of a felony (forcible rape, perjury etc.) and Fox ignored the story, I would agree with you.
But they have yet to do this whereas CNN, ABC, NBC and CBS have all significantly covered up for Clinton. Even the Lisa Myers' report concerning Juanita Broddock was downplayed. I don't see O'Reilly doing this if it were a GOP rape scandal. O'Reilly, in fact, may be the most prominent critic of the Catholic Church -- a conservative institution -- concerning the pediastry matter.
Journalists, regardless of their political views, are supposed to look for scoops and provide the viewers or readers with information relevant to maintining their freedom -- which includes the character of one's leaders.
CNN et al are biased to the left to the point of dishonesty. Fox tries to play it straight and only appears biased since the leftists control the agenda.