Large university libraries probably hold books about religions which contain idol worship. (They might also hold books about sexual immorality and murder.)
Libraries make books available to the public. If I put a book about idolatry on its correct shelf, perhaps I'm helping to make it available to readers. Those readers, in turn, might then be inspired to start practicing idolatry, or to increase their idolatrous acts.
For the purposes of this question, please assume: If you volunteer at a certain university library, you'll be required to put idolatrous books in their correct place on the shelf, at least occasionally.
If so, are you allowed to volunteer at such a library?
Note: The halachic information you read on this website is not guaranteed to be correct. Please consult your own rabbi, for multiple reasons.