Usually not a huge fan of the books that explain the fall of Western Civilization but I did like this argument, as put forth by Susan Jacoby (or at least by the reviewer):

anti-intellectualism (the attitude that “too much learning can be a dangerous thing”) and anti-rationalism (“the idea that there is no such things as evidence or fact, just opinion”) have fused in a particularly insidious way.

Usually pundits/scholars base the latter portion of the argument on the rise of relativism. I like this characterization better. Oftentimes, high school teachers fight a losing battle in trying to get students to appreciate multiple points of view without allowing the “everybody has their own perspective so nobody is really right or wrong” stance.