Rape is a terrible thing, and the author of the books wants his readers to know that terrible things do happen, and somethimes people get away with it. However, they're in the books. For the most part, the show has stuck to the book. And most book readers have loved HBO for that. Having said that, people that have read the books have kept their opinions on the very few changes in the other thread. But this one seems rather significant because it could possibly change the dynamic of relationship between the Lannister Twins.
If the producers and director were trying to leave the audience guessing as to whether or not it was consentual, they did a terrible job.