And that's the problem most people who have criticized the scene in this way have with it. From a narrative standpoint, neither character really needed this rape to motivate them. For Sansa, the Bolton's are responsible for the deaths of most of her family. For Theon, he's been tortured tremendously, and just seeing Sansa in that castle and knowing the horrors that awaited her would have easily been enough to wake him up. Them working that angle would have been interesting, and something actually different for the show.
Instead, we get another shock value rape scene that does nothing to push the story forward in a way plot elements already introduced wouldn't have worked fine for, and that told us nothing new about any of the characters involved. And worse, people are thinking this is OK because it'll serve as Theon's turning point. Well, people are fine to think that's OK, but you can't think it's good, fresh writing. "Rape of female character as motivation for adjacent male character's story arc" is one of the most problematic and overused tropes there is, and GoT really didn't do anything to elevate it.