Actually, it is impossible to have a neutral arbiter. The problem isn't one of perceptions and allegation of bias. Most statements either are not objective (Trump is a bad president) or are objective in theory but cannot be determined (Trump intended to dig up dirt on his political rival). Nature doesn't provide a zero detent, so there is no way to be a neutral arbiter.
The problem with Big Tech determining what is and what is not fake news isn't censorship, it is that they have proven time and again that they are no better at determining what is true than we are. Big Tech doesn't have some rigorous technique, they pass the buck to media companies. Media companies pass stories along like Chinese whispers... nobody bothers doing investigative reporting anymore because it's too expensive given the shifts in the marketplace. So on a per-story basis, only a handful of people actually have direct knowledge, and as humans with biases they relay their interpretation of that knowledge. Everyone down the line parrots the bias unknowingly. The only way we find out the mainstream media is wrong is when another person with direct knowledge took perhaps a video and posts it on YouTube. Unfortunately for that poor sod, he gets the video taken down as fake news.