A term that originated on Usenet, Godwin's Law states that as an online argument grows longer and more heated, it becomes increasingly likely that somebody will bring up Adolf Hitler or the Nazis. When such an event occurs, the person guilty of invoking Godwin's Law has effectively lost the argument.
Excellent!
I am starting to consider a “Fox’s law” - when presenting facts to a liberal, and their comeback is telling you to stop watching Fox news.