Hero worship

During a conversation with a friend about cinema books once, I found myself defending the hagiographical approach. Our relationship with films and film stars can be very intense, intimate and proprietary; if an author chooses a favourite subject to write a whole book about, and then invests time and effort in doing so, why expect the result to be detached and (loathsome word) "objective"? Surely it's understandable if the writing is full of fanboy passion.