Maybe a slightly different example will help understand the logic?
Let's say NewsCorpA likes Trump and Spacey.
NewsCorpA publishes their usual stuff saying they're both cool and good, but one day they post an article saying Trump did something bad. Because they have every reason to like Trump it seems more likely to me that the article has a genuine criticism (not to say their reasoning is good. E.g. He's not racist enough), but that doesn't have any bearing on the other, usual, articles about Spacey.
In other words it's kinda the inverse of "if someone hates someone and says something nice about them, it's probably genuine" so kinda "if someone likes someone and says something bad about them, it's probably genuine"
Maybe a slightly different example will help understand the logic?
Let's say NewsCorpA likes Trump and Spacey.
NewsCorpA publishes their usual stuff saying they're both cool and good, but one day they post an article saying Trump did something bad. Because they have every reason to like Trump it seems more likely to me that the article has a genuine criticism (not to say their reasoning is good. E.g. He's not racist enough), but that doesn't have any bearing on the other, usual, articles about Spacey.
In other words it's kinda the inverse of "if someone hates someone and says something nice about them, it's probably genuine" so kinda "if someone likes someone and says something bad about them, it's probably genuine"