yep, the whole "who decides on the truth?" thing is extremely irritating. Do we throw out every court case now because apparently it's impossible to determine what is fact and what is fiction, or to establish common rules or guidelines for conduct? We've been doing nothing else for thousands of years.
It's more of a, "what is fact and what is opinion," rather than, "what is fact and what is fiction."
"9 out of 10 doctors recommend Colgate," is a fact when Colgate picks the sample of doctors. A trained eye will realize that's actually an opinion, while it's designed to represent a fact. This works because people's opinions can be shaped by presenting an opinion as a majority.
This technique is probably one of the most commonly used and it has many variants, such as, "Your child could be in danger of edibles in their Halloween candy." Technically a fact, but actually a disguised opinion.
Treating everything as if the consequence of getting it wrong is sending an innocent person to prison doesn't make any sense. Courts don't even do that. They use different standards when imprisonment isn't an option.
and I don't see how this doctrine is violated if companies like twitter act with caution when in doubt. (which they have every incentive to do)
But nobody says "Johnny the crazy axe murderer gets to roam free because who is to decide what is true or not?" Which is just about where the speech debate is for some people.