Fake violence vs real violence is purely psychological
If you view death in real life for the first time it will be mind numbing and jarring to all of your senses. However, if your brain thinks it's fake, you instantly become desensitized. Real people who commit war crimes irk are trained to completely dehumanize victims before they kill them so that they don't catch feelings.
In a video game you know it's fake so your brain doesn't get attached unless you really like who dies. They're two completely different fields that rarely influence each other unless you're delusional or mentally ill. The problem with video games and any form of violence is that it creates opportunistic thoughts in mentally ill people. If you have some sort of personality disorder and you are kept in a completely loving and caring environment with no violent video games, th chances of you doing something violent are astronomically low. However, if you're mentally ill and you're constantly exposed to violence and abuse you become influenced by it. This is the most common background for all honor students or Flash Mobers