Poe's Law:

Without a winking smiley or other blatant display of humor, it is impossible to create a parody of Fundamentalism that SOMEONE won't mistake for the real thing.

In other words, no matter how bizzare, outrageous, or just plain idiotic a parody of a Fundamentalist may seem, there will always be someone who cannot tell that it is a parody, having seen similar REAL ideas from real religious/political Fundamentalists.

The law also works in reverse: real fundamentalism can also be indistinguishable from parody fundamentalism. For example, some conservatives consider noted homophobe Fred Phelps to be so over-the-top that they think he's a "deep cover liberal" trying to discredit more mainstream homophobes.

From Urban Dictionary and Rational Wikipedia