Mindless and heartless

I have been thinking about historical novels and realized that all the ones I have read circles around one topic: war. About what started a war, what ended it, which killed who, how people lived through wars and after them. I came to the conclusion that history is made by wars; wars are what makes up history.
We, human beings, like to believe that we have brains to think and that we actually use them and are always so grateful to God for that. In reality though, we do all have brains but most are not used, left to rot more like.
It's all part of being a human being, most people don't appreciate what they have unless they worked hard to get it or until they lose it, we don't have brains because we worked any harder or because we are special, we have brains only because God gave them to us, just like a leg or skin.
We all have hearts too, that's what's supposed to make us alive (does not using it make us less alive?) but how many use theirs to feel?! (Okay, feelings are from the brain but it's simpler to think of feeling and thinking as two separate things even though in reality they are intertwined it would be complicated to separate them.)
I therefore came to the conclusion that most people can only use their mind or heart but very rarely both, so at any people in time a person would as a rule be heartless or brainless, choose your pick. There are some exceptions to that one of which would include people who can use neither.
If people actually think and feel them why are they killing in every corner of the earth! Why is there more hatred that oxygen in the air! I didn't realize I'm so angry about what is going on in the world until I started writing this. I feel lost and wish I can find answers, how can someone hurt a child, let alone kill on? How can anyone kill for the sake of killing, just to make a point!
With all the fury in me, I find it easier to live believing that man is doing what he's doing because he is not thinking rather that doing it because he thought long about it and believes it's the right think to do. How would I tolerate living in such a world otherwise?!