When should an author leave out his/her politics from a story?

Joyce Carol Oates' story about twin brothers caused some consternation, because the "demon" brother is identified as a conservative politician. So when should authors leave their politics out of a story? Apex's Michael A. Burstein has a well-thought-out response.

Top image: cover of Stories, edited by Neil Gaiman and Al Sarrantonio, art by Tom Gauld. [Apex]