And that's the problem. The people who make up this stuff can see when it's being shared, and commented on, and what resonates most with people. They can write up the perfect crazy story for my Mom and Uncle to talk about like they have done for the past 60 years.
I can go in and say this is fake, don't believe anything you read from this website or facebook page, and sometimes they'll believe me. But that doesn't stop the content from flooding in.
The only thing I can think of is getting people to stop using Facebook altogether.
We haven't really figured out how to address these issues. The best we've got now is an initiative by Metro called Viralgranskaren (~"viral post inspector") that debunks myths like these. [1] What I think needs to happen is for the education system to start putting a larger emphasis on skepticism and source criticism. These skills and qualities are crucial for a 21th century liberal democracy.
[0]: http://www.snopes.com/sweden-bans-christmas-lights/
[1]: http://www.metro.se/nyheter/viralgranskaren/ (sadly only available in Swedish, it seems)
My hope is that now that it has become very noticeable in the US maybe they'll do something about it, but it's entirely possible they do nothing for the reasons you said.