In library school, future librarians are taught the saying “every book a reader, every reader a book.” They are not taught — by example or otherwise — to point out the flaws in books. Nor are they taught to impose their own preferences on those who come to them for help. Professors — who are in the same business, the spread of knowledge — could learn something from this. John Taylor Gatto has pointed out that the same teenagers who are disruptive in class are well-behaved in libraries.
I think this blog proves your point (though it might seem at first to contradict it) about the typical attitude of librarians (read the about page): https://awfullibrarybooks.wordpress.com/
Fascinating point. However, librarians are very selective as to what they will allow in their libraries.