Why does he do that? Are there really no equally kind multitalented interesting girls he could get instead? Is he just so kind that he's willing to go through all that because it's clearly the only way the girl will ever have anyone, and he'll sacrifice his own well-being to charitably give an awful person a nice relationship?
I assume this is a big reason why that sort of movie is considered a chick-flick - girls watching it empathise with the girl-character, and so see "oh a lovely man showing his undying love, how nice", but guys watching it try to empathise with the guy and see "ARGH WHAT THE HELL IS HE DOING, SHE IS AWFUL TO HIM, IT MAKES NO SENSE." And as someone I know grumbles fairly often, this sort of movie makes for horrifically unrealistic expectations for a girl, that you don't have to do anything even remotely decent to get your own perfect Prince Charming out of the blue. And then if he actually does come along, don't forget to treat him like crap!