I'm being a bit spoilery here, but I think both Game of Thrones incidents I mention are pretty widely known and have been discussed at length elsewhere. But I'll warn you anyway in case you're one who hasn't heard about them.
I'm on record elsewhere as being a non-fan of George R. R. Martin's massive A Song of Ice and Fire fantasy series. In short, I think that it started out with some level of appeal that left town as soon as it became clear that Martin's desire to create a fantasy series in a more realistic medieval-era world made for a grotesque and depressing reading experience.
No surprise, then, that I'm a non-fan of the HBO adaptation of the books, Game of Thrones. The series uses Martin's novels as an overall source material but has changed some characters and incidents, eliminated some others and compressed much of the narrative. It's currently in its fifth season and has recently drawn a lot of fire for two incidents that are ugly, creepy and have brought show-runners a lot of flack.
Incident one was in a May episode that ended with the rape of Sansa Stark at the hands of her new husband, Ramsay Bolton. I've not seen the episode, but if there is any accuracy in the many descriptions I've read, then we are not talking urgent-bordering-on-rough wedding-night passion. The complaints were that the scene was gratuitous and used not for any really necessary character development in Sansa so much as in service of another character's storyline. The effective double-dehumanizing of the Sansa character brought the feminist geek culture site The Mary Sue to the decision of no longer recapping or hosting discussions about the show. Detractors noted that the show had altered the scene from Martin's books, changing Bolton's victim from one character to another, so it was not a case of claiming fidelity to the original narrative.
The second incident occurred in this past Sunday's episode, in which the character Stannis Baratheon, at the urging of a priestess of a fire-god cult, burnt his daughter Shireen alive as she screamed to her parents for help. Stannis had been portrayed as genuinely loving towards his daughter, even though she had suffered from the disfiguring disease greyscale. Many more people swore off the show, especially since this was also a scene not in Martin's books.
A writer at the pop culture and review website Pajiba raised the question in a recent article (no links because they hold to the custom that profanity equals authenticity, and it doesn't) of why these particular incidents might be the ones that drove viewers away. A couple of seasons ago, the guests at a wedding were all slaughtered, including a pregnant young woman stabbed numerous times in the stomach. The first episode of the show featured a brother forcing his sister into a politically advantageous marriage and depicted their resultant coupling in a manner very like rape. The incestuous brother and sister couple had sex near the laid-out corpse of their son in a manner also very like rape. Though Martin's book made both scenes appear much more consensual, the TV show didn't.
The Pajiba writer suggests that the tolerance for GoT depravity has dropped because the show quality has declined. The current seasons are drawing from Martin's more recent books, which both bestseller bloat and the underlying hollowness of his premise have weakened. They lack the narrative strength to give context to the horrible things both book and show talk about. I think he's onto something there, although my analogy is different.
As I see it, both Martin's books and the HBO show are a mixture of a spoonful of dog crap in a five-gallon bucket of ice cream. Up until now, fans of the books and the show have been training their minds on the parts of that phrase that contrast "spoonful" with "five gallon bucket," But of late, the serving line has gotten closer to them and their bowl is on its way down the table, and they find they can't look away from the "dog crap" part of the sentence. So I get it, and I sort of sympathize, but I also would be remiss if I didn't point out that the dog crap was there all along.