As a Librarian, it is considered the worst sin to completely remove from existence any work of writing, art, media, documents, or anything similar. There was a lot of agonizing after 9/11 regarding books that discussed making explosives, but in the end, those books weren't removed,.
Smaller, public libraries tend to weed out their collections simply due to a lack of space. But, if you really are searching for something, just search
WorldCat and you are bound to find it somewhere. Most library systems have access to Interlibrary Loan programs where you can borrow a book from another library if your local library does not have it.
Worse case, if you are willing to travel, most libraries are open access or by appointment so that you can travel to them to use their collections. In some cases, the librarians might be willing to photocopy a few pages from a rare book and send it to you for a small fee to cover the cost of printing.
Then there are online sources of books
just to name a few.
That doesn't mean that rare, one-of-a-kind books, documents, to manuscripts haven't been lost forever. Wars and terrorism throughout history are notorious for destroying cultural places, including libraries.
But the current movement is to digitize as much as possible so that, even if something happens to the original print version, there will at least be a digital backup.
Bottom line, it's not the books or media themselves, it's how they are used. A book on explosives could be used to make weapons for acts of terrorism, or they can be used by people in the demolition business to legitimately take down old buildings or other structures like the recent Trump Casino implosion in AC.
You can have someone reading books on Nazi Germany in order to emulate them and march around with torches, seeking to terrorize non-whites. Or you can have someone, a historian, a student of history or political science, or a scholar in other areas, reading the books in order to create a new understanding of how movements like this evolve as a way to learn from and understand the past and how it affects the present.
Even Culturally insensitive works, especially as viewed through the modern lens, may have value. It's all in how you view it and how you use it.