I think you, Ryu, like Lemon are looking at this too much within your own set prisms.
Last time I checked, Rupert Murdoch supports a Democratic candidate, Hillary Clinton.
Colbert and Stewart are entertainers who feed off the establishment media and often times do a fun job at it. But please don't tell me seriously that's where your 'hard news' comes from. O'Reilly is a commentator who you probably think all their fans or followers are just in line with him. Have you watched his show? Is he entertaining? Yes! Television is about entertainment but don't stop there - does news have to be dispassionate, shallow, robotic, etc.? O'Reilly is largely targeted because he has passion, he challenges all his guests, and prides himself on presenting accuracy to his audience.
In any instance, they (Stewarts/Colberts and O'Reilly) are not relative; Stewart makes a living being a heckler and a joker, O'Reilly has been a reporter and commentator for decades. But you don't see it that way and I can't make you. As it stands, you're not going to give him a fair chance because, in line with your past posts (Ryu), you don't care to give any benefit to anyone who is deemed "rightwing" or doesn't agree with your views.
Colbert (a man who I find very difficult to understand since he plays another persona all the time) mocks The Factor (and has been on the show various times) because he knows there's an audience who, regardless of whatever O'Reilly says, is going to please those who believes he's a 'bad guy' or one whose just open to be mocked. That's a shallow and narrow outlook; to view everything as one big joke and that nothing nor any information is valid and that everything is just relative. I would even argue is much of Colbert's and Stewart's mostly ignorant, cynical audience believe Fox News is bad, even before they've watched a program on it!
I would permit that, yes, Fox News is a conservative-leaning news media outfit. But I accept it being there to have as something of a contrast to a without question left-leaning media dominance not only on TV but in print. And it's not only American media but much of the greater world press. You know what? I don't think I've ever seen more of an attempt at presentation of both sides in any news venue. I think Fox tries the most and since the norm is decidedly "liberalism" dominated by 10 to 1 (in print and TV), Fox is seen as an unwelcomed invader who, uh oh, maintains #1 ratings to a once almost exclusively monopolized media.
It's not about "fact" as you claim, it's about ideology and those who often don't formulate opinions objectively.