You want to look at the decay of Western civilization? It's mostly the unexamined absorption of Marxist ideas.This came to mind immediately:
Now, I'm one of those people who live too much in books and theories, and, as such, I can tell you why they're absorbed and treated as gospel: it's because they make internal sense. This is not the same as having even a glimmer of real world application, of course, but they satisfy the minds of intellectuals by dividing everything into categories and presenting a (false but deceptively smooth) system for historical change and, in general, sounding REALLY plausible.
Take the Marxist theory of value. It is utter nonsense of course. The idea is that what gives value to something is the labor put into it. You can see how this would appeal to Marx, or, indeed, to any intellectual. Laboring forever over a book that sells one copy is now a genuine, bonafide "injustice". The book is valuable. Just look how much work you put into it.