We are very fragile creatures (I assume that we are all human- any aliens reading this, feel free to let us know? 8-). We can die if we lose more than half of our blood, or are exposed to temperatures, pressures or humidity outside of a rather small range, given the conditions on much of our homeworld. We kill each other over even less variation. Sometimes simply being different, being other, is enough to turn a crowd into a killing mob. We are creatures of fear and of hope; of hate and of love. All very kumbayah, I suppose, and as cynical as I am, I don't expect human nature to miraculously change to 'humane' overnight, although one can have hope, and work for something better, always...
I am a bit of a hypocrite. I know, at the end of the day, that all I really care about are me and mine. You and yours are your family and tribe, related to you by blood or by spirit. If you understand these... limitations to the human design envelope, if you will, then per-maybe-haps you can short-circuit the bad, enhance and increase the good.
I know that I am capable of killing, and probably of murder, too. I've lived on a farm, I have on occasion seen to the Thanksgiving turkey (generally called T-bird and Christmas, BTW, and no, I never got very attached to those pea-brains!), or rabbits, ducks and chickens. I eat plenty of meat, and I know how it is an industrial product, wherein a lot of things best left unsaid and un-thought-of happen, including, at some point, somebody killing a poor dumb animal whose purpose was always to have been food. So, getting finally to the point, I can and I would kill, for me and mine, for our table, or to protect our home.
At some point everybody needs to stop, take a minute, and think about exactly how far you would go, in the extreme, for you and yours. Answer yourself honestly and be prepared to someday live with that answer.