I do accept that I have a considerably more liberal view of this than most people, but there is literally zero correlation between video game and real world violence, and the only reason I can see to keep a game from a child is if it will cause them mental trauma. Halo will not.
That's generally not true. There are a number of studies that show a correlation espeically when focusing on M rated games, 18+ games, shooters in general or games with specific violent factors.
Of course all that correlation shows is that violent angry people like to play violent angry videogames. It should be no surprise that people who like to go out and punch people like games in which they punch people, and TV shows in which people punch people, and books about punching people.