Elan if you don't like it, that's fine, but that's your desicion, why should anyone make that desicion for you? I read stuff at least as adult as aSoIaF when I was twelve and certainly don't think I suffered from it.
If anyone had tried to censor me (the only time that happened was when a librarian didn't want to allow me to lend some books) it would only have made me try harder to get those books.
Personally my first argument against censorship is that it doesn't work, it's just another way of advertising.
My second and far more important argument is, that yes Kid can be hurt by too much violence and perhaps sex too, in books or films, but in my opinion, it's not reading/seeing it that hurt them, but being left alone to cope with it.
Look at the old fairy tales, they are violent like hell, but they were told by granny in front of the fire, and granny was there to assure the kids all would be good in the end, to explain things, to comfort kids.
The problem with videos and some kids today is, that videos have replaced the grannies, they show the violence, but they give no comfort, nor explenations.
If parents try to censor what their kids read, the kids will get more curious about the forbidden stuff, but will be barred to go to their parents for comfort and explenations.
If you don't want your kids to read somthing, don't buy it for them, but if they get it elsewhere don't make a fuss about it, try to keep their trust, and be there to pick up the pieces in the worst case.
In the end you can't protect you kids against the world, as hard as you try, but you can try to make your kids ready for it.
Personally I would have no problem reading Dark materials to some 8 year old (and would have problems to give it to some 16 year olds) but better to read it to your own kid, and be there for questions, than having the kid read it on it's own, without anyone to answer questions.