Logical fallacy of the day

RationalWiki:

No True Scotsman is a logical fallacy by which an individual attempts to avoid being associated with an unpleasant act by asserting that no true member of the group they belong to would do such a thing.

The term was coined by Antony Flew, who gave an example of a Scotsman who sees a newspaper article about a series of sex crimes taking place in Brighton, and responds that no Scotsman would do such a thing. When later confronted with evidence of another Scotsman doing even worse acts, his response is that no true Scotsman would do such a thing, thus disavowing membership in the group "Scotsman" to the criminal on the basis that the commission of the crime is evidence for not being a Scotsman. However, this is a fallacy as there is nothing in the definition of "Scotsman" which makes such acts impossible.

A modern example may be found at the would-be Conservative encyclopedia, Conservapedia. The founder of the site, Andrew Schlafly, has repeatedly used this fallacy to defend his personal concept that Conservatives, by definition apparently, do not practice deceit. When confronted with examples of deceit on the part of Conservatives, he routinely disavows that these individuals are Conservatives at all, on the basis that Conservatives do not practice deceit. He instead assigns them to the group liberal, regardless of evidence to the contrary. The use of this fallacy is underlined by the fact that prior to revelations of deceit, the same individuals would have been hailed as good Conservatives.

Phrases such as "un-American", "unChristian" or "inhuman" are widely used in politics and media to distance onself from a subject, defining them as outside the bounds of what the speaker considers to be truly 'American', 'Christian' or 'human' behaviour. These phrases strongly suggest the No True Scotsman fallacy, since the use, for example of "un-American" to describe specific political activities by some American citizens implies some special definition of "American" beyond mere nationality.

(Via LGF)