Rape is part of human behaviour so it certainly can have a legitimate role in stories. It happens in wars, on the streets, in intimidation, in business, and in families. To deny it is to restrict to only one side of humanity. Rape is more than plot, it can simply be a person’s character, if they’re isolated with another in a vulnerable situation….or, coping with a character’s past (ie, the victim). And how the story’s society responds to the victim/perp, that can illustrate the world.