You obviously haven't played against my 4 year old son. When he's on, he's on. But most of the time he plays the pacifist, "You my best friend, right?"
Yeah, I haven't played a 4 year old... One because none of my family are that young, and two because the game is Mature... that guy is either bluffing horribly, or has very poor morals to let a four year old play violent games..