Godwin's Law (or Godwin's Rule of Nazi Analogies) is an Internet adage in two forms...
1) the longer an internet thread continues, the probability of a comparison involving Nazis or Hitler approaches 1"—
2) If you mention Adolf Hitler or Nazis within a discussion thread, you’ve automatically ended whatever discussion you were taking part in.
The Crossfire Variant ...the longer a discussion of politics goes on, the probability of a claiming that Obama is a liar approaches 1
Proposed Crossfire Law.. If you change the subject of a thread to make gratuitous shots of questionable validity, you have ended the discussion. (I think I'll start observing and imposing this on myself. I'm sure we can count on several members here to highlight every perceived violation on my part.)