There's a difference between using information about an author to help analyze the thought process behind their work and using information about an author to prejudge their work. I can analyze Sir Arthur Conan Doyle's writing based on his belief in spiritualism, but that isn't the same as labeling Sherlock Holmes blasphemy. You are confounding evaluating purpose and evaluating quality. If I was writing an essay on the origins of TempleOS, then knowing the personal life of the creator helps. If I'm evaluating the quality of the software, then information on Terry is irrelevant.