> Without a winking smiley or other blatant display of humor, it is utterly impossible to parody a Creationist in such a way that someone won't mistake for the genuine article.

(the original phrasing)

But it works for other things as well. When a position is known to be, or believed to be, accepted by a significant number of people, and someone expresses that position, without knowing them it's impossible to tell if it's sarcastic or sincere. Even if it's presented in a somewhat exaggerated form, there are people would still hold some of the views the GP expresses.