IANAP (...Not A Psychiatrist), but a great many people who are enthusiastic readers (especially of novels) seem to imagine close relationships between themselves and their favorite authors, extensively fabricate details of the authors and relationships, and become very emotionally invested in those imagined relationships.

Hence the anger and feelings of betrayal when an actual author's identity, behavior, etc. fail to match those of the reader's close and trusted (but quite imaginary) friend.