I think the library should respect your wishes, -- it is, after all, not a museum, -- but why, really, would you be concerned with such exposure?
In my view, it is far better to inform the prepubescent child of the look of the adult body of both sexes, if only to remove the sense of mystery when puberty hits.
I have no problem with a prepubescent child seeing nude art. I do hae a problem with a pubescent child being exposed to it.
Perhaps I should reread the article to get the age of "child" clear.