Godwin's Law and the Lunacy of Cat Banners.

"There are many corollaries to Godwin's law, some considered more canonical (by being adopted by Godwin himself) than others. For example, there is a tradition in many newsgroups and other Internet discussion forums that once such a comparison is made, the thread is finished and whoever mentioned the Nazis has automatically lost whatever debate was in progress. This principle is itself frequently referred to as Godwin's law. It is considered poor form to raise such a comparison arbitrarily with the motive of ending the thread. There is a widely recognized corollary that any such ulterior-motive invocation of Godwin's law will be unsuccessful."