The Guardian denies the existence of media bias... LOL
They probably think they're unbiased too!
That's pretty dumb - even I conceded there's a liberal bias in many reporting institutions. However at this point there are enough conservative reporting institutions that you can pretty much get whatever news you want to see.
You can't claim that "they" are out to get you if "they" are a small proportion of a large field of disinformation.
The gist of Lucia Graves' op-ed (I assume it's an opinion piece) is "Yes, mainstream American media are decidedly tilted toward the Left, but that's not very important since the average media consumer seeks out a couple of more conservative news sources."
If you've going to say that ("we're biased, but it's OK because folks seek out alternatives"), then you cannot legitimately call out those alternatives for being biased the other way. Sauce for the Goose...