The Week has published a screed against the low moral quality of Game of Thrones, Game of Thrones is bad — and bad for you. Obviously there is something to this insofar as one can see a coarsening of entertainment, or at least a decline in the stylized aspects of the depiction of reality.
But one of my initial reactions is that much of the narrative that we value from the past was not particularly PG. If you read The Harlot by the Side of the Road: Forbidden Tales of the Bible you see that the “Good Book”, in fact the only book many read front to back by many after the Reformation in Protestant Europe, has some quite unsavory tales. The story of Judah and Tamar in particular is hard to digest from a modern Western perspective because many of the elements are understated and workaday. Greek mythology is no better obviously. From Zeus raping Leda, Achilles throwing a fit because his sex-slave was taken away, to the tradition of Agamemnon sacrificing Iphigenia.
In some cases the shocking aspect of ancient stories is because moderns have different values. Slavery and concubinage were taken for granted during the period that the Hebrew Bible and Classical mythology crystallized into the forms which came down to us. In other cases I presume that it was unlikely that small children were going to ever read the original stories themselves, so sexual elements that might confuse were probably omitted in some oral tellings.
This is not to say that Game of Thrones is a modern masterpiece. But some of the disquieting, and frankly perverse, aspects of the narrative are only shocking if your standard is the relatively antiseptic literary fiction which one finds between the Regency and the cultural revolution of the 1960s. That is the aberration in human history, while gritty genre fiction much closer to primal human storytelling.