Why is rape romantic?

When I was thirteen my I went to Barnes and Nobles with my mom and she gave me permission to buy one book. Since there weren’t any new Gossip Girl books or any of the other trash I liked when I was thirteen, I picked up a historical romance novel that looked pretty good. I believe it was called “The First Princess of Wales” and it was about Joan of Kent, a real historical figure. The story inside seemed to have nothing to do with Joan’s life, though. Joan and her husband Edward, The Black Prince, were a very romantic couple in real life, and he married her despite a lot of opposition and it seemed they were very happy together. No where in the history books does it mention a rape. But in the novel, Edward kidnaps and brutally rapes  the underage Joan (in real life she was older than him but in the book he’s implied to be significantly older than her), and she responds by falling head-over-heels in love with him. 

Of course, after that I put down the book, disgusted. It seemed really wrong. I wasn’t really a feminist at age thirteen, but everything I’d been told about rape made it seem like it’d be really offensive for women who had gone through that for it to be portrayed in that light. I told my mom what I’d read, and she wasn’t the least bit surprised. “You used to see that kind of thing all the time in romance novels when I was your age.” She even told me there was a couple like that in a soap opera she used to watch called General Hospital. He raped her, but the ended up married with children and are still together in the show. In fact, they actually have a large fan base online even today. 

For some reason, that plot device seems really degrading to women. Going back to the medieval belief that women are possessions to be “taken” by men. That book gave the impression that Joan had only resisted because she needed to be “broken” and that once that happened she became a docile woman eager to return Edward’s affections. The book was set in the thirteen hundreds, but it was written about a supposed “great love story”. In real life, if a woman falls in love with a man who rapes her, it’s Stockholm Syndrome and the victim would probably need therapy to get over it. If not, it certainly wouldn’t develop into a normal or healthy relationship and she wouldn’t love him in the same way women normally love men their involved with. It seems like a dangerous message to spread and a mentally unstable young man could even see it as a sign he should rape the object of his affections. Why would anyone think rape is romantic?