Video game violence is a necessity in modern America in order to keep real life violence at a minimum. Human nature dictates that we be violent in order to accomplish self-preservation of the race, kill or be killed. Modern America is relatively safe, and we have plenty of food, which means that we can't advance without suppressing our violent instincts.
For most people, this isn't such a big deal. Education has helped society learn how to cope with these feelings, but it can't help everyone. Having a release for these feelings helps keep people from finding a more dangerous, more violent outlet.
Many people have, at some time in their life, felt the desire to kill. It's part of being human. Would it not be better for society to give this person a bloody video game killing aliens, where no real person gets injured? Or would it be better to cut out this distraction, allowing the person to possibly act out on these desires and hurt or kill another human?
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You get the idea. I didn't feel like writing out a closing paragraph. Oh, DO NOT use what I wrote. I whipped this up in less than 10 minutes simply as a counterpoint to what you came up with simply as an example. If you need any more examples, search for posts made by Tilley and Mensen, they are both very good at arguing.
Whatever you do write about, I suggest sticking with being either for it or against it. Don't write it showing both sides, it will weaken your argument.
Something else you could argue about in a very similar fashion to what I wrote is how strip clubs are a necessity to cut down on sex offenders.