But there might not be a better word for the latter scenario. Surely, few oppose libraries from “banning” pornographic books, so some level of discretion must be used by administrators.
How about age-gating?
[1] Free speech non-profit mostly focused on literature.
In the context of this thread, it would be calling a book a "banned book" because it is banned in some school libraries, despite being widely available everywhere else. Akin to calling dogs a "banned pet" because they are banned from post offices. Technically correct but highly misleading without context.
https://en.wikipedia.org/wiki/Banned_Books_Week
I suspect that the same applies to most of the words that came to your mind; they're just being used in contexts you politically disagree with and therefore it's a "misuse". (Seinfeld's "soup nazi" was a misuse. Putin's use of the same word is a misuse. Descriptions of modern nationalist movements and the powers that support them are descriptive.)
There is a concept for pets called "banned breeds" (e.g., "pit bulls") that are similarly politically motivated in the same way that book banning happens.