Where the story first originated. Who was the first person to say it.
Marking articles which are clearly incorrect is probably a good start.
The sky is checkered like a chess board if you are in the right part of Minnesota on a Monday evening. <= Fake News
Your example works for my idea too. If you are the source for "The Minnesota checkered sky theory" then the buck stops with you and an investigation of your credibility would be damaged.
I mean 'you' in the rhetorical sense of course.
The thing I'm talking about is something like a reputation score for news sources.