I respect the various reactions of different people to this scene. It was very tough to watch, and I continue to be uneasy about what the writers are doing with this storyline. But I'm going to continue to watch, and hope that they can redeem it soon.
I've found the TV show OK, but lacking a lot of the depth and complexity of the books. The books have a lot of implied rape - as one might expect from a violent and feudal war-time setting - but not much depicted. This particular scene, though, *is* in the books (*). It's actually worse in the books.
So: is our beef with Sansa's decision to go along with the plan for her to marry Ramsay? Unlike Jeyne, Sansa knew what it meant, and could have chosen otherwise. She has knowingly chosen to submit herself to repeated rape in order to find the opportunity to avenge her family by destroying the Boltons: both Ramsay and his (equally monstrous) father Roose.
Or is the problem with the depiction of the rape? I thought that was the best thing about it: not gratuitous, not titillating, and a refreshing change from the usual HBO approach. Would it have been better left to our imaginations, even more than it was? Just omit the last 30 seconds of the episode? Perhaps.
Or is the root of our unhappiness that we are shown the rape's immediate effects on Theon, not on Sansa? This, again, is straight from the books, but I think it works better there (where we have spent a great deal of time with Theon) than on the screen (where our focus is switched from Sansa to Theon at the end of the scene). Theon's misery is real, but is neither one thing (Sansa's experience) nor the other (our imaginations, a curtain in the wind). It's a distraction.
I think that ultimately the distress I myself felt is because - unlike the greyscale, the dragons, the sword fights and the horse lords - it's all too real, all too easy to connect. Life is full of people submitting to violently abusive situations, to rape and humiliation, for their families, for their positions, for money, or just because they have given up on themselves and cannot imagine a way out. That's the horror.
(*) Albeit with Jeyne Poole rather than Sansa, but surely that's irrelevant, otherwise we are just complaining about bad-things-happening-to-characters-we-li