“Fake News” Is in the Eye of the Beholder

no, it's not. Some news is objectively false and has been repeatedly, and conclusively, disproven (e.g. Obama was born outside the US).

> Much like the word “terrorism,” the phrase “fake news” will be manipulated to accord with whatever pre-existing ideological commitments its newfound opponents already espouse.

possibly, but while it may be hard to say which stories are 'true', it is definitely possible to identify 'false'/fake ones. See Popper's concept of falsification: https://en.wikipedia.org/wiki/Falsifiability