If you want to go far back enough, it used to be a job for men not considered manly enough to succeed at proper manly professions. I'm not sure the quiet part ever applied, except in stereotype and fetish.

I assume your collection is there for the researchers to consult in their coursework, or for the research that one of the faculty does. Also, university library and therefore your content is presumably created toward adults who can consent to see the material.

I'm not surprised that the preacher burning the books was also watching the movies. Rather than admitting to hypocrisy, it would be easy enough to claim that it was an intelligence-gatherong trip. (That, and there are a lot of places that believe their preachers are inherently holy and incorruptible, so it wouldn't matter if they saw the thing the rest of us were supposed to stay away from.)