There are some parents that don't like their children playing violent video games. I'm not going to tell anyone how to raise their kids, but I will say that there's a lot about life that kids can learn by playing first-person-shooters, all of which are violent to some degree.
I was playing Star Wars: Battlefront yesterday morning, and one player on our team repeatedly would stop in an ice tunnel hallway, right before it opened up into a large ice cave. This would prevent everyone behind him from getting into the larger room and taking cover. Time and time again, he would do this, resulting in the death of several of his teammates. We lost the game by a significant amount.
Only a "Newb" would do something so strategically dumb. But here's the thing: all gamers advance from the newb level to something better, by doing two things: learning how to become a better player by oneself, and learning how to become a better teammate.
We all know people who are that newb in our work environment: the person that through their own incompetence, slows down the whole team. In a video game, kids have the luxury of communicating in a non-PC fashion, so if you're really hurting the team, people will tell you, in no uncertain terms, and you'll get a stronger incentive to learn how to help the team, instead of hurting it. In real terms, video games are perhaps the strongest teacher of teamwork for kids, outside of organized sports. The thing is, there're plenty of people that will help you become better, if you ask.
Most video games, and especially first-person-shooters, also have reward systems. You might get an added item that gives your gun the special functionality that you want. It might be something as little as a different color that you can make your gun stock. But the harder it is to get that bonus, the more value it holds to the community that plays that game. Some bonuses require more than a hundred hours of play. They're held up as badges of prestige. You have to work to get it. Those that learn how to play the game better, and those that have better natural skill, can get those bonuses faster, just like in the real world.
Most first-person-shooters allow a tremendous amount of customization to your character and/or weapon, so that you can work towards creating what you need to do well, based on your unique skill set. You get to work on your comparative advantage, again, just like in the real world.
Another important lesson that first-person-shooters teach kids is the risk/reward trade-off. Newbs all tend to take too much risk. They'll run out into the open where they are sitting ducks. They'll go up against three enemies at the same time, dying before they can even take one out. You see it again and again with players who have very low-level scores. However, as their skill advances, they learn how to adjust their risk levels. Perhaps they can go up against those three opponents, once they're good enough to do it, but that usually requires a tremendous sink of time to learn how to be that good.
First-person-shooters have a wide plethora of life lessons inherently built into them. I'd suggest that their benefits far outweigh their negatives, even for young kids. Of course, adults should be playing them, not only for the tremendous amount of fun they are, but for the cognitive exercise that they exert on the brain.
Killing newbs by the dozen--it's not only fun, it's teaching young kids valuable life lessons--lessons better learned in a game than in the ugly environment of real life.