Man or mango?

Movie: The Book of Love. All I can say is any woman who would cheat on Simon Baker is insane. No, wait, that's not all, after all. Baker's character was a kind, decent, innocent chap whose worst fault seemed to be a habit of correcting other people's grammar. At the end of the movie, everyone else seems happy or content with their lives, while he remains devastated. What kind of message is this?