As I have noted previously, my son has been diagnosed with Autistic Spectrum Disorder and the line between real and make believe is fuzzier with him than with most children.
My children have a specific and unfortunately intimate relationship with death and violence, as we lost a baby almost a year ago (miscarriage), a great grandmother a few months before, and have had close friends suffer through violent assaults. All of that information was not kept from our children.
I respect the intelligence of my children, but they are NOT born as fully formed and mature individuals, capable of internalizing any and all stimuli and using that to make value judgments at an early age. I have a role to play, as does their mother.
Children on our street regularly pretend to murder each other, using play weapons modeled after their FPS games. They describe said murders in loud voices, and detail the tactics they are using, what parts of the body they are aiming for, and what effect their weapons are having on the body.
None of these children are older than 12. Say what you will about value judgments, something is influencing their thoughts and actions, and in a way I do not find to be positive.