A lot of playing in nature between animals is essentially mock combat. Humans aren't really any difference, you put some kids in a backyard and somebody is getting whacked with a stick.

Being able to confine that to video games, which can also have a positive social and problem solving aspect to it is way better than just being bored and picking fights at a bar.

Violence and conflict is natural, a kid who exhibits worrying behavior while playing a video game is going to show that same behavior somewhere else if you take away the game console.

I totally get where you're coming from, but I don't think it desensitizes people anymore than horror movies, living on a farm, or growing up somewhere where actual violence is common.