Analogous to the eye-roll that careful students of American history make each time they hear Republicans call themselves "the Party of Lincoln” is the facepalm one should make upon hearing how the mainstream media is "biased."  

People of a certain age cannot fail to draw comparisons between the network news of now versus the network news they grew up with 50-60 years ago. This is the mistake. They no longer can and do compare, and what passes for news now on networks funded by advertising is not even a passing attempt at what journalists would call "journalism." 

We all got used to "free,” and as long as there were only three networks (speaking of the US here), it didn't matter much to the advertisers that bankrolled the programming what their political slant might be because the demographics were basically the same. In other words, the sales figures studied by media buyers (the advertisers and the agencies that represented them) had little correlation to the political demographics of the viewership. Just numbers of viewers for particular shows and time slots, nothing else. 

Once the number of networks exploded (thanks to cable TV) and media ownership rules relaxed (alongside the demise of the Fairness Doctrine in the US, which mandated the broadcast of opposing views), it started becoming mandatory to show advertisers what kind of viewership they could expect for their media buys. They couldn't just fling money at every national news outfit. So of course it suddenly became imperative to align with a particular political ideology. Parroting a party line, overtly or not, became a key part of keeping a reliable audience that advertisers could scientifically assess for the purposes of understanding cause and effect in their media buys. And of course products came to be developed with an ideological demographic in mind.

And as more radio and TV stations saw this necessity, they then started ideologically sorting themselves for this very purpose: to remain quantifiable to those who paid their salaries. And while the on-air talent may have some affinity for the politics of the network they represent, the ownership, in spite of what they may claim or who they might associate with, does not. They only care about the business of selling ads: the bottom line.

That’s why it’s fatuous to express dismay regarding the integrity and/or bias of any commercial network news at this point in time. The viewer is not their customer - the advertiser is. Content, with whatever biases are baked in, is a loss leader designed to get you and your spending habits into their store. CNN doesn’t care about the Democratic platform; Fox doesn’t care about the Republican platform. Well, they care only insofar as it helps drive advertising metrics for their sponsors. If their sponsors came to them in unison and said they wanted to sell to the opposing viewpoint demographic, they would do their best to adjust the on-air bias to suit that. 

Journalism that doesn’t depend on advertising as a funding source is the only one with the potential for an honestly-derived bias (meaning, the journalists and editorial staff assembled themselves around a point of view, not a business model), and is the only kind worth agreeing or disagreeing with.

And it’s like shouting at the sky when it’s raining to berate the so-called “mainstream media.”