Gandhi was like Hitler because he too was hated by Churchill. Lord Adonis is like Hitler because he’s also commissioned road-building. Harold Shipman is like Hitler because he’s also a murderer. Co-presenter of Homes Under the Hammer, Lucy Alexander, is like Hitler because she also has opposable thumbs and is therefore much more like Hitler than, say, a toaster or Droitwich. And lacrosse is like Hitler in that I think they both only have one ball.

David Mitchell, March 28, 2010. The Guardian.
Before you start mouthing off about Hitler, you better know your Nazis.

Reductio ad Hitlerum, also argumentum ad Hitlerum, (dog Latin for “reduction to Hitler” or “argument to Hitler,” respectively) is an ad hominem or ad misericordiam argument, and is an informal fallacy. It is a fallacy of irrelevance where a conclusion is suggested based solely on something or someone’s origin rather than its current meaning or context. This overlooks any difference to be found in the present situation, typically transferring the positive or negative esteem from the earlier context. Hence this fallacy fails to examine the claim on its merit.

The fallacy claims that a policy leads to—or is the same as—one advocated or implemented by Adolf Hitler or the Third Reich, and so “proves” that the original policy is undesirable. For example: “Hitler was a vegetarian, so vegetarianism is wrong.” The tactic is often used to derail arguments, because such comparisons tend to distract and anger.
-From Wikipedia, “Reductio ad Hitlerum

For a complete list, please consult the internet.