The Silo Effect

Columbia Journalism Review:
While concerns about political and media polarization online are longstanding, our study suggests that polarization was asymmetric. Pro-Clinton audiences were highly attentive to traditional media outlets, which continued to be the most prominent outlets across the public sphere, alongside more left-oriented online sites. But pro-Trump audiences paid the majority of their attention to polarized outlets that have developed recently, many of them only since the 2008 election season.
Attacks on the integrity and professionalism of opposing media were also a central theme of right-wing media. Rather than “fake news” in the sense of wholly fabricated falsities, many of the most-shared stories can more accurately be understood as disinformation: the purposeful construction of true or partly true bits of information into a message that is, at its core, misleading. Over the course of the election, this turned the right-wing media system into an internally coherent, relatively insulated knowledge community, reinforcing the shared worldview of readers and shielding them from journalism that challenged it. The prevalence of such material has created an environment in which the President can tell supporters about events in Sweden that never happened, or a presidential advisor can reference a non-existent “Bowling Green massacre.”

It's the narrow-mindedness, stupid.

While you're trying to see country and party and candidates from a perspective that includes as many aspects as possible, Alt-Right Conservatives (eg) are being fed a steady diet of binary purity, narrowing the perspective down to some pretty ridiculous bumper sticker sloganeering that sometimes contradicts itself.

"My guys are always and only good which means your guys can't be anything but always and only bad."

But there's a kind of Orwellian contradiction to it too. If I start with that binary, but then apply the negative component to "the system of a corrupt duopoly" (eg), then the benefit of the smear accrues to whoever I can make you believe is standing against whatever's being smeared. So while the overall approval for Congress is low and constantly beat down by relentless generalized attacks on "idiots in da gubmint", I can condition you at the same time to see "our guys" as fighting the noble fight to hold back the onslaught of the ruinous agenda of tax-n-spend libruls and blah blah blah.

Remember that while the approval numbers for Congress as a whole are dismal, 90-95% of these people get re-elected. A big bunch of the reason for  that on the GOP side is gerrymandering and voter suppression, but let's put all that together with a message of "they all suck, but my guy's one of the good ones - he's lookin' out for me".  Now we have that the cult thing - isolation and indoctrination, which is where that thing about The Breitbart Sphere comes in.

And not to get all Both-Sides-ey on ya, but it's become a lot more visible on the left as well. The big myth being peddled the hardest is that Hillary didn't win because "she's not Democrat enough". "She's a creature of Neo-Liberalism." "She abandoned traditional Democratic Party values". None of that is flat-out untrue, but it illustrates for me that the Purity Warriors are revving up, and I'm not going along with that because I see it as having full potential to be translated to little more than fulfillment of the Both-Sides prophesy.

Analogy Alert
We're almost completely off the pavement on the righthand shoulder, and we have to steer  to the left to keep from hitting the bridge abutment up ahead. But if we yank the wheel and over-correct, we run just as big a risk of veering all the way over into the left lane and being smushed head-on by a cement truck.

The point being that The Logical Extreme is where good ideas go to die. Keeping it down the middle isn't sexy and it's not terribly satisfying and it can feel just like losing, but it's what we have to do in order to sustain this little experiment in self-government.

In the end it all depends on factual information, and the ability to test the information so we can make accurate assessments of its veracity.

Let's review:
In the presence of confirming evidence
the absence of conflicting evidence,
the statement is more likely to be true

I the presence of conflicting evidence
the absence of confirming evidence,
the statement is more likely to be false