Both parses of the English that Trump spoke and unfalsifiable.
Even the completely made up posts (eg "The Pope endorses Trump") are going to be extremely difficult to distinguish from a piece of actual breaking news.
An algorithm will end up having to look at the source - and yet many in this election campaign argue that many of the traditional media outlets post false news too.
I disagree with this: they may have their slant on news ("Trump did/not say Mexicans were rapists"), but they generally don't post complete fabrications.
I still aren't at all convinced that actual false news is a real problem - I'd say there was a much bigger issue with differing interpretations of events.