Michael reminded me yesterday of something I've been meaning to post on my blog. In fact, I thought I had already done so, but a quick search for "nazi" and "hitler" reveals this was yet another case of false memory syndrome.
The rule of the title is "Godwin's Rule (or Law) of Nazi Analogies." If I have the time, I often like to scan the comments that follow controversial articles I come across on the internet, so I'm well acquainted with this principle in action.
This has been around for quite some time. Mike Godwin, lawyer and writer, described his Rule in a 1994 Wired article:
As an online discussion grows longer, the probability of a comparison involving Nazis or Hitler approaches one.
He started seeding his "meme" in online discussion groups, once the invoking of the two key terms had appeared, and soon the Rule took on a life of its own. Just think of the healthcare town meeting discussions in the US this summer: how quickly and pointlessly the dialogue degenerates to the name-calling level.
The other side of the political divide would provide a good corollary. It takes no time for liberal to become socialist and socialist to become communist. Reminds me of my father's John Bircher brother, who treated me to the following faulty syllogism when he found out I was engaged to a Brit:
The UK is a socialist country.
Socialists are the same as communists.
You're marrying a communist.
Why bother arguing?
PS Another of Wikipedia's fascinating little tidbits:
The character "Michael Godwin" in The Difference Engine by Bruce Sterling and William Gibson was named after Godwin as thanks for his technical assistance in linking their computers to allow them to collaborate between Austin and Vancouver.