Barack Obama

Reductio ad Hitlerum, also argumentum ad Hitlerum (Latin for "reduction to" and "argument to" and dog Latin for "Hitler" respectively), is a term coined by conservative philosopher Leo Strauss in 1951.[1] According to Strauss, the Reductio ad Hitlerum is an informal fallacy that consists of trying to refute an opponent's view by comparing it to a view that would be held by Adolf Hitler or the Nazi Party.

According to Strauss, Reductio ad Hitlerum is a form of ad hominem or ad misericordiam, a fallacy of irrelevance, in which a conclusion is suggested based solely on something's or someone's origin rather than its current meaning. The suggested rationale is one of guilt by association. Its name is a variation on the term reductio ad absurdum.

Reductio ad Hitlerum is sometimes called "playing the Nazi card."[2] According to its critics and proponents, it is a tactic often used to derail arguments, because such comparisons tend to distract and anger the opponent.[2]

http://en.wikipedia.org/wiki/Reductio_ad_Hitlerum