Sorry for the wall of text, but I think that these points are worth bringing up.
I based my vote on the desensitizing effect, not on what you were talking about in regard to making people more prone to violence. I'd say that I have become desensitized to violent images, and some forms of real world violence. But that doesn't mean that those who have become desensitized are more prone to violence. The logic doesn't flow, desensitization does not lead to one committing violence acts themselves, merely they aren't emotionally affected when they see others commit violent acts on others.
I will say though, that my opinion, as well as the others who have and will post, are really irrelevant. If I had taken the time to review the research in the area, for and against it, I'd feel much more confident in my response. Right now I just have a general sort of idea of what I think about it, which is useless. If you want to write a paper on this you should review the peer reviewed research, a unqualified persons opinion is useless.
This is why I have a problem with how you worded the question. One 'believing' or not 'believing' in a scientifically confirmed phenomena doesn't change whether it is true or not. I would suggest you reword it to, "Do you agree with the hypothesis that there exists a desensitizing effect, and moreover, do you think that this makes those who are affected more prone to committing violent acts themselves." I really have a problem with the term belief in a scientific context. That word has far to much baggage and really takes away from the scientific aspect of it, it subtlety implies that something has a 50/50 chance of being true, which is almost never the case in science. I would highly suggest that you use another word when you hand in the report.