People, people, people, you have to understand one thing about this game first before you write anything in reference to it: this game is meant to be a harmful outlet in a harmless setting! What I am trying to say is that the game is supposed to be violent because that is what we are as humans: VIOLENT, FURIOUS CREATURES. Why do you think children fight over toys? Why do men lie and cheat and steal? It is the crater to our morality, our innate human nature, the primal instinct to serve the id, the "selfish" center of the human psyche.
You must realize, that Grand Theft Auto IV is only playing on the fact that this id is one of the most controlling factors of our lives; our own primeval instincts usually serve to be the most useful (anyone heard of fight or flight? The base center of human survival?). Essentially what Rockstar Games is doing is allowing us to use GTA IV as an outlet for our uncontrollable human nature; so why is it bad for children? IT IS NOT (if said children can distinguish this as a harmless, fantasy context rather than reality). Children need an outlet for their own primal selves as well (kid punching a pillow: releasing his anger, preparing himself for the next hour, and a new day). Letting out violence is what we as humans must do in order to survive, and what better way than staring at a box, a harmless screen comprised of billions upon billions of triangles, colors, and scripting codes, where all of our violent intentions can come true, so that we can fully release the tension, the blinding furies of life?
Grand Theft Auto IV is an excellent game, and once you start playing it, you do grasp one major concept: everything we do has consequences. Say for instance, you break into a car on the game: well, the alarm was set, and goes off, and a cop happens to notice this. You have two choices: you could either run, and have the cop follow in pursuit, where you are likely to be caught by some means of governmental force (i.e. search helicopters or even the S.W.A.T. force), or you could stay put, get arrested, and follow through your sentence (which in the game is called getting "BUSTED," where you lose all your possessions, a large portion of money, and are siphoned of all your time for the next couple of days [in game time, that's quite a while]).
So really, are we dealing with the next "killing sim" as some parents like to call it? Or has Rockstar finally provided such an imaginary context in which we can express real and tangible emotions and outbreaks of our own humanity, providing we can discern the imaginary from the real (which is another case of perception of it's own), finally producing a resolve to everything we experience throughout our lifetimes? The message is there, but it can't make you listen to it. That's up to you.