What kids? its an 18 certificate.True about the film bit but you dont play the part in a movie.
COD is a war game, i can't see the fun in killing people as they run next one they might put kids in 2 that might be fun
So what if you dont "play that part" in a movie?
You may watch it and read it in a book, and given good enough imagination, you can place yourself in the head of those characters.
Personally it didnt offend me at all , and I was happy to play it.