I used to quarrel over peoples’ sources. Links from sketchy websites, second hand anecdotes, statistics: whenever people would employ these to a persuasive end, I’d point out the unreliability of the source, hence invalidating their point.
I was right. And ineffective.
Fake news didn’t start with the internet. Just ask anyone who’s heard the tale of the fish Young Tom caught or the description of Joe’s girlfriend, who you wouldn’t know because she goes to a different school. The more interesting question for Young Tom and Joe is not “Is it true?” but “What is at stake for you in the story?” Treating a tall tale as an incorrect fact misses the point; it’s a story about the person telling it, and it should be handled according to the conventions of narrative, not forensics.
YoRocko! 
Narrative, not forensics… I have a new mental motto for dealing with this. Last time it happened, I received some dodgy stories with an e-mailed “Can you believe this?” and took it literally. The stories were about supposed repairs to Notre Dame, so I went to a French web site I like to read and listen to for practice — and I found the story of the real repairs. I wrote an e-mail back saying that no, I couldn’t believe it, and telling what I’d found in French. I would not take “Can you believe this?” literally from everyone, but this time it was “Be ready to account for what you believe” time.