It's the fear. Fear is behind our human perversities. We've been so afraid for so long, we've grown up with the fear, as a species. And traditionally we're not allowed to mentioned it, because it is taboo. And frightening, of course. So we pretend we're not afraid, and even trick ourselves into thinking we aren't afraid.
The fear is unacknowledged, but the energy of the emotion must naturally be expressed, so the fear changes, and often turns to anger.
As with fear, the emotional energy of the anger must find expression. But anger is commonly socially unacceptable and it may be possible to find ways of masking our anger, ie self medication with alcohol, tobacco, drugs, or even extreme physical activity. However, this anger is very commonly expressed in violence.
We have the phylogenic hidden fear, turned to anger, which finds expression in violence.
The tyrant is afraid; he masks his fear with anger; he must find some way to expend the energy of this emotion; but he is a civilised man and must justify his rage; he tells the world that he is threatened by a very dangerous enemy; he goes to war against his peaceable neighbour.
It seems convoluted, but it's really very simple.
The tyrant has no justification at all to attack his neighbour; but it does seem that war has been seen as legitimate and civilised activity for thousands of years; a way of dealing with the painful emotion of fear-turned-to-rage. And I am completely sure that unconsciously all this is well known.
Our violence against the world and each other is not natural or justifiable.
I strongly suggest that we learn to acknowledge our legitimate phylogenic fear. It takes courage but George Frankl said, 'It's alright to be afraid but you must be very brave, you must have courage.' Listen to George.