I’m not really sure what people expected from Facebook here. The oldest of newspapers struggle with these kinds of judgements (until they just decide to stop caring and cater to a certain political side). It is not reasonable to expect Facebook to get it right with any consistency, if there even is a definitive correct answer to begin with.
Facebook has a policy that they put in place that's fairly reasonable, they have outside fact-checkers they acknowledge as experts. They deliberately set aside the mechanism they put in place to avoid this kind of nonsense.
It is entirely reasonable to expect Facebook to apply the policy that they themselves created in order to avoid having to make these kind of calls.