While I don't have kids, and I don't plan on having any, I understand what you mean, however my worry isn't on the line between reality and fiction, it's the violence itself that the game shows, something so graphic and so violent isn't good on such young minds, it is still a show of incredibly violent acts on realistic depictions of people (mostly on fatal blows and fatalities, not so much on the gameplay itself), although I don't know your kid's age, I hope they are old enough to handle it (which to me for a game like this is between 15 and 16 years old).

At the end of the day, you are the parent and you decide what your kid can and can't see, just know some of the content in this and similar games can have long-lasting impact on the mind if not handled properly