That's not quite what I was getting at, but I guess I can give you an example. I used to roll my eyes at right-wingers complaining about the "liberal media". But now I think they have a point. Just look at the dirty laundry Wikileaks aired.
I don't know. The DNC emails were less "skeletons in the closet" and more "dirty laundry". Disgusting, depressing, for sure, but there's nothing there that I would call surprising. If anything, the amount and extent of media collusion revealed by the leaks was actually less than I expected.
As for the "liberal mainstream media" phrase... well, its history put aside, the accusation in itself
isn't exactly wrong. CNN, NBC, NYT & co do tend to favor views that are seen as "left-wing" in the context of American politics, and while it is true that "reality has a liberal bias" on science-related issues, it cannot explain everything. Coupled with an inherent slant towards the societal (not just political) establishment they are an integral part of, this typically translates into tacit support for the Dems.
What makes it eyeroll-worthy is that the loudest accusations of liberal bias tend to come from people who either trust, work for, or are propped by media outlets on the other side of the fence that have rather flimsier claims of
basic trustfulness, let alone objectivity. It is almost never used as a warning to keep a critical and analytical mind, and almost always as an incentive to use the "right" sources of information.