Godwin's law
/GOD-winz law/ · noun · Hacker Culture · Origin: 1990
Definitions
An internet adage asserting that as an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one. Originally formulated by attorney Mike Godwin as a counter-meme on Usenet to combat the trivialization of Holocaust comparisons. In internet forum culture, invoking Godwin's law traditionally signals that the discussion has devolved past the point of productive dialogue.
In plain English: The idea that any online argument will eventually lead to someone comparing the other side to Hitler or Nazis.
Example: "Fourteen comments in, someone compared the new app store policy to fascism. Godwin's law remains undefeated."