If one took a nine year old girl on vacation and exposed her to a group orgy many might say that was a bad thing. If you encouraged her to give a hand job to a adult male, just to see what it was like, the parents would probably face charges, as well as other people involved. It is not the girl has been violated, she has not been penetrated, but most would agree that psychological damage done would be non-trivial. Most would also agree that there would be no way for a nine year old girl to consent to such a sexual act, so it is by definition non-consensual sexual activity. Therefore charges would be filed.
On the other hand, it seems perfectly legal to put an Uzi in the hands of nine year old girl for the purposes of recreation. And when the girls kills another person, there is no concern about her long term psychological well being. No concern for the fact she will have to live her entire life knowing that she killed another person. No concern of what kind of parents would allow the risk of such a thing happening.
I guess it is the nature of our gun crazy culture that we want to censor people being beheaded, pictures of non-erotic children, but nothing wrong with allowing young children, who cannot consent, to participate in our death rituals. No one censors the blood leaving the body, the last moments of death, as long as the goal of high profits for the gun manufacturers is met.