Sorry, but saying "that's just how human nature is" is another way of saying "I'd rather not think about it and come up with a real answer because the fact is it'd make me a hypocrite". I find it quite offensive when people say stuff like that, because by saying something like that is human nature, people are saying I'm the same way (being the fact that I'm a human), and I'm not (proving that it isn't human nature).
ok, i think i dont get what you mean. let me give you a hypothetical situation: a guy busts in your house, and your mom is in there. he has a gun. he gives you a gun, and then sais "if you dont kill me right now, im gonna blow your moms brains out." so, what do you do? are you saying that you were wrong to kill him even though you were protecting your loved ones because he has a family and they would be sad? i dont get it. im not trying to be sarcastic or anything like that, i just really dont get what you mean.