In all honesty, yes, I do believe videogames can cause violence, same as films, music, and every other media form. However, the sheer majority of games will not cause violence. Kirby is not going to convince kids to become domestic terrorists and neither is Sonic, Rayman, and so forth.
The key here lies in the glorification of violence. Games like Manhunt supposedly have a system that rewards players for how brutally they kill their opponents. This caused quite a ruckus a while ago after they pushed to get Manhunt 2 banned after it was supposedly linked to a gruesome murder in the UK. Of course, this was vastly blown overboard, and I've heard the copy of the game was instead found to belong to the victim rather than the aggressor.
I'm not saying Manhunt here is an offender here. In fact, as I have said, videogames do not cause violence so easily. It requires a number of factors. First of all, the desire for violence must already exist within the player, and it must be presented in a way that must specifically be appealing to them. These two factors are already largely outside of what a game developer intends with their works and the former is more or less entirely impossible altogether.
If a game developer, however, was to specifically evoke feelings of extreme aggression in their works - such as portraying a sympathetic serial killer as the main character - it becomes closer and closer to causing violence if the player is already unstable. Moreover, there are plenty of tricks to make to player violent, all psychological and, again, largely outside of what a game developer intends to do. The goal of a game developer is not to invoke violence.
This does not mean a malicious person would not be able to achieve so. If they had the knowledge and opportunity, they could easily create a game that causes the audience to have thoughts of violence, but this is not something yet achieved with any videogame. The media often takes the idea overboard when they speak of violence in videogames.
All in all, it's entirely possible that videogames can cause violence, but not how people often think. The idea needs to already be there in the player's mind and cannot come to light at all unless the game presents violence in a way that is appealing to them. Kirby, Sonic, Rayman, et cetera do not cause violence. I have not played Halo or GTA but I highly doubt those games will lead kids to start bloody revolutions either. The idea is taken out of hand in modern journalism.
