>For instance, in the first study stories were either favorable or unfavorable about either former President Barack Obama or current President Donald Trump. Favorable stories reported that the target had donated $50 million of their personal fortune to selected charities, while the unfavorable stories reported that the target was facing criminal charges related to voter fraud in the 2016 Presidential election. Participants then made "legitimacy judgments" of each story, rating how much they believed the story to be true, reliable, and trustworthy.
I'm pretty left-wing, so my biases would presumably lead me to believe the favorable story about Barack Obama, and disbelieve the favorable story about Donald Trump. [1] How does that work out in practice? Well, at first glance it seems pretty accurate. Trying my best to abstract away from the context of this study, I'd give about 2% credence to the story about Trump, and maybe 35% to the story about Obama (does Obama even have $50M of personal wealth?). Hypothesis confirmed, right!? Not exactly.
It's true that I'm answering these questions according to my existing beliefs about each politician. But those beliefs aren't simply the result of "bias". I came to those beliefs for reasons. For example, I know that Trump is infamously stingy. [2] Him donating 50 million in personal wealth would be a real shock to me, and for good reason. I know a bit less about Obama, but I don't have a strong reason to think he's stingy, and I do vaguely recall some news indicating that he has made a number of large charitable donations. [3]
So yes, both liberals' and conservatives' judgments are based on their beliefs, and if you put those people in a position where they have to use those beliefs to judge claims in the absence of other evidence, they are liable to believe lies. But one of these groups believes the truth - that Obama is more charitable than Trump - and the other does not. In other words, much of the liberal susceptibility to fake news can be explained simply by pointing at the justifiably higher credence they have in many pro-liberal stories.
[1] I'm relatively well informed, so I'd give ~0% credence to either story about criminal charges. But if one of these stories were true, it would probably be true about the person who's already under investigation for his actions in the 2016 election.
[2] https://www.washingtonpost.com/politics/trump-boasts-of-his-...
[3] https://www.forbes.com/sites/danalexander/2017/02/06/obama-d...