<h4 class="dechead">On One Hand: There is a Definite Correlation
CNN reports that Dr. L. Rowell Huesmann has performed extensive research in this field and found that children who play video games are more prone to violent behavior. Violent video games contain imitable behavior and also desensitize them to violence. Several sources, including Cognitive Daily, report that the U.S. Army uses video games in part to desensitize adults to violence.
On the Other: Alternative Interpretations Exist
A competing view becoming increasingly popular among psychologists is that violent individuals may simply be attracted to violent video games. The games themselves are not a cause but rather an expression of violence. However, if someone plays violent video games regularly, it does not necessarily mean that said person is prone to violence or other negative behaviors.
Because of the vast amount of conflicting data on the subject, it might be better to address circumstances case by case. If you feel a child or loved one's personality is being altered by overconsumption of violent media, you should take action and talk to them about it.
No. Assuming there is no underlying mental/physical defect, it's going to depend on how the child is raised by the parents. I grew up on Bugs Bunny cartoons, GI Joe, Atari, hair bands. Turned out just fine. And that's because my parents were actually parenting, not being my buddy.
Yes. Violent Video games has been correlated with an increase in people voting for Republicans.