This seems like a hot topic.
My point of view:
Portraying unhealthy sexual practices and relationships - nonconsensual, abusive, exploitative - is not necessarily bad. Such relationships exist and are an unfortunate part of the human experience. Writing about them taps into audience knowledge and for some, personal trauma, which bridges a bond between story and reader.
However, I do think that romanticizing them is dangerous. The written word is powerful. For some vulnerable or obsessive people, such works will contribute as part of a greater whole to beliefs in the acceptability of such conduct. And people who want to do things that are not generally accepted as moral will search out such sources to reinforce their position. The advent of the internet has allowed for self-selected echo chambers, reinforcing nonfactual and/or nonmoral (see, e.g. torture) beliefs and reinforcement of those those beliefs has demonstrably led to believers committing acts of individual and mass violence.
So, yes, I was deeply troubled to hear about a high school science teacher in a small town 20 miles from me not only having multiple crushes on his students but belonging to a secret site which was full of romanticized stories of forbidden love between teachers and their high school students. That was a recipe for disaster.
I don't think GoT romanticizes violence or sexual assault, but rather is attempting to tell a story in a historical time period context which is authentically dangerous and violent. At some point in writing, such things can become gratuitous and that is something an author should be mindful of.
With respect to gay books for children, it is dumb to suggest that reading such a book can change someone's orientation, but a lot of people who take that position have a retrograde, unscientific belief that there is no such thing as sexual orientation - homosexuality is a sin which can afflict everyone. More jaded and knowledgeable homophobes want to suppress such books because they want to keep gay kids from feeling comfortable enough to embrace their sexuality. Modern rationality realizes that homosexuality is objectively morally neutral, though.
