Difference between animal and mankind

What I thought about characteristic difference of slaughtering between mankind and animals.Some say that human being can't stop killing each other since it's our instinctive nature,but in my opinion there is a distinct difference.While animals killing is a kind of ecological cycle seen in ecologic chain that is rather harmonized with the nature,human being is a rational creature that is not designed to kill each other.Therefore,the more our society becomes advanced,the more rational behavior we're required.Besides it,let us imagine nuclear war.It obviously has devastating and negative affect to our precious planet earth,so it can be undoubtedly said that war affair would be destroying the environment significantly.

That is what I thought when I watched a popular TV documentary program "Planet Earth".