Just like other animals, we cannot transcend our nature.
That is incorrect. Humans have transcended ''their nature'' on numerous occasion. You live a sedentary lifestyle and have no significant knowledge or skill to survive in the wilderness. We have created entirely artificial environment just for our own benefit and drastically changed our way of life. While there might be some limits to our capacity of self-transformation, we definitely have transformed our way of life and ways of thinking. Plus, any argument on what ''human nature'' runs in in the problem of defining what is human nature and sometime brushes aside the capacity of humans to reduce and/or transform how this nature expresses itself.
In my opinion, violence is part of human nature in the sense that we all have violent impulse and that, statistically speaking, it will express itself in a destructive way at one point or another. The question is how often and how badly. Religion, like any other major belief system, has fueled and excuse the most terrible expression of violence by exciting prejudices, insulating people from guilt and justifying it's use. The overwhelming majority of people are averse to violence, especially radical displays of it like murder, rape or pillaging. It takes special excuses and justifications to make it pallatable and religions often come with excellent and easy justification for those.
