I think you're getting off the point a little. I was not stating that psychology etc isn't in part responsible but that the basic cave man instincts and physiological actions and reactions are just as much a part in acts of violence ... for your additional information I am not American and and am interested in ALL aspects as a matter of personal interest. Have a look at my previous posts and i think you'll get where I'm coming from. For example the one on violent reactions from babies. .. who have never encountered violence.
It's an emotive subject and to make people think, consider and take on board additional information is the aim. If a person has their view and refuses to acknowledge that there may be other effects of any new information (in any subject) that is entirely up to that person.

I think the comments of circumcision is a little off topic and again from personal experience i can say not all of your statement is entirely a fact for everyone. .. but that is not a discussion to have on this post which is about the chemical response to using a weapon.
But i thank you for your input and information. It's always good to get other views. :)