Fundy loon

From RationalWiki

Note: If you were looking for information on aquatic birds from the Bay of Fundy, you're in the wrong place.

"Fundy loon" is a contraction of the tautological, pejorative expression "fundamentalist lunatic".

A "fundy loon" is someone who is considered, by rationalists, to be absolutely, totally, stark raving mad by virtue of his or her primitive beliefs.

These poor people have often been so indoctrinated since childhood that no amount of logic or facts can relieve them of their affliction.