It's not even appropriate to call such actions censorship. Public libraries have limited space and can't carry all published books. Most books must be excluded and decisions should be made based on the reading interests of a community.
The idea that there is ANYTHING wrong with removing Heather Has Two Mommies from the shelves (if that had happened) and replacing it with a book more want to read is absurd.
Censorship is when a community tries to give input into what books it wants in its library.
Appropriate decision-making is what it is called when a librarian decides for the community.