If the press have the editorial freedom to chose which of their reporters articles they publish -- be it factual, opinion, or even outright biased -- then why shouldn't other private platforms have the same editorial freedom?
The "who" in your "who gets to judge?" then becomes a simple answer: the platform owners. The uncomfortable part is that some platforms have a larger impression on people than others. But short of government intervention -- which is a hugely unpopular option in America -- that's just the markets working the way you guys want your markets to work (ie given the psychology of confirmation bias, if platforms were to focus on unpopular view points their viewership would diminish).
That's the paradoxical part of all this. The same freedoms are being used in both cases but in one instance it enforces principles you believe in and in the other instance it erodes those principles. But you cannot have one instance without having both.