Ok, lets start with statement number one
he also chose to play the video game itself, which lead to him killing the person.
The complexity of human thought and understanding is far to great for us to generalize. We can never know to what extent the video game influenced him in doing so, so we try to reason what the possibilities are of the video game doing it. Thinking about any times I went into anything near a blind rage, it was compounded things that overwhelmed me. With this knowledge, I think that it is impossible to claim that a single cause will result in a human action.
Anything that happens in a video game can happen in the real world
This statement is somewhat ridiculous considering I've seen other statements saying that video games are designed to display impossible situations. I'd seriously like to see Sonic face off against Dr. Robotnik in real life.
If you enjoy shooting people in video games, it's sounds like you'd enjoy shooting them in real life.
If we want to get really technical, you aren't shooting people, you are shooting targets designed to look like people, aliens, robots, etc. Furthermore, try jumping off a cliff in a game and sailing to the bottom before you get a game over, that can get pretty amusing... Now try doing that in real life... fun...
You cannot even compare violence in real life to that in video games. Whats real is so different and means so much more than whats not real. You die in a game, you get another life, you die in real life, what happens next?
Violence in real life you learn what not to do, because it teaches you that it's bad. In violent video games, you can learn what not to do, but only if you know it's bad.
Violence in real life doesn't always teach you its bad, as a matter of fact, violence in real life is far more likely to affect you than a game. If we consider for a moment that killing someone in a game
can affect you, then what happens when you hear about a murder in real life. If beating up on enemies in a game can influence you, than how much more would being beat up in real life affect you.
Reality is so much more than virtual reality. Kids may not always know the difference, but they will most certainly be affected more by a real life event than a video game.
And on the subject of children vs. violent games... indeed a responsible parent should be careful about traumatizing their kids with gory games, but to single out games as a killer danger and ignore all the other real life and present dangers is ridiculous.