By way of Entertainment Weekly, we get the author's response to charges he uses sexual violence against women gratuitously.
His reasons:
Historical accuracy:
The books reflect a patriarchal society based on the Middle Ages.
Artistic license:
Most stories depict what I call the ‘Disneyland Middle Ages’—there are princes and princesses and knights in shining armor, but they didn’t want to show what those societies meant and how they functioned.
The books have strong, relatable female characters:
I have millions of women readers who love the books, who come up to me and tell me they love the female characters. Some love Arya, some love Dany, some love Sansa, some love Brienne, some love Cersei—there’s thousands of women who love Cersei despite her obvious flaws.
I find the last of these the most compelling because what no one seems to be mentioning is that the books are actually quite feminist.
The women are all trapped in roles due to the mores of the patriarchal society. They struggle to overcome these limitations.
Cersei wants power--real power--but since it's denied to her she has to go the route of Lady Macbeth and pull the strings behind the scenes.
Brienne of Tarth is a cross-dresser who is the only one in the book adhering to the virtues of honor and loyalty that the males are supposed to, but don't uphold.
Because there is no place for women warriors in this world, Arya Stark makes herself invisible—again a way a woman can have power without seeming to have power.
Given that so many fantasy and sci-fi books feature heroic males and damsels in distress, this seems to me like something in Martin's books that we should be praising.