In many ways, the internet has taken the urban legend and launched it into hyper-speed. Sure, we still said things like "Santa Claus was invented by Coca-Cola" before the internet existed, but now the time from inception until general acceptance is much shorter.
The cartoon also addresses the closed loop phenomenon, whereby false information posted online becomes its own "proof," showing, again, the dire need to teach students how to think critically when conducting internet searches.
I think this process is actually pretty simple, at its core, and it involves getting students to consider the source, what organization is publishing it, and who the writer actually is. The latter is, of course, impossible with Wikipedia, which is written by anonymous authors. That is another reason why, as I say here, it should never be cited on a paper.
It is mainly good as a casual tool to get your feet wet on a topic, not as a direct source allowed to speak in your paper.
That would be like turning your group presentation over to the dude who never showed up to your group meetings. Don't do it.