Nobody is saying here that EVERY child that has been sexually abused will abuse or that EVERY abuser has been sexually abused. I was abused by someone that was abused as a child. I was also abused by someone that had never been abused in any shape or form. Some do, Some don't. Plain and simple. But it does have lasting effects on a child. And he had to have learnt that behavior from somewhere, by seeing, hearing, or experiencing it himself. And his lack of apathy and his sense of not even trying to defend his actions suggests that he thinks this behavior is fine. So with that said, his parents need to be investigated to see how their 12 year old little boy has learnt this behavior. Either way, it's the parents fault, no kid is born a rapist.
Now don't get me wrong, if a grown man was to do this, then I would not point fingers at his parents, but as a parent you are supposed to protect your kids from these kinds of things. At 12 years old he shouldn't even know HOW to rape someone. I mean I'm all about teaching your children about sex. But because they know about sex doesn't mean that they are all of a sudden some little horny bastards.