Speaking of the ever-expanding political lexicon, Portable Matthew has coined a simply fabulous new term that I intend to begin using from now on: Fringebaiting:

fringe·bait·ing

Pronunciation: 'frinj-'bA-ti[ng]

Function: verb

Definitions:
1. To assert that the mainstream of the political left or the political right should answer for the crimes perpetrated by their respective political fringes.

2. To claim, without evidence, that a popularly accepted ideology or belief is responsible for acts committed by extremists.

3. To argue that dangerous extremism only exists on the side opposite to one's own political views .

4. To contend that political views are illegitimate if held by both the mainstream and the political fringe.

Simply magnificent. A perfect word for an all-too-common tactic, and a sin committed by practically every political party and partisan position. Even, alas, by myself now and then. Even though I knew in my heart I shouldn't be doing it, I now have a conscious tool to remind myself when I see it, or am tempted to do it.

Not that mocking the fringe is necessarily a bad thing, especially when the fringe gets into excessive prominence. It's a bad thing when comparing someone's opinion to the fringe is used to marginalize his argument.

Matthew has more to say on the subject that you might want to read.