It all boils down to what your basic philosophy of life is. I believe there is a natural law higher than all laws of man. That law is that everyone is entitled to their own life, liberty and property, assuming they do not try and encroach upon the life, liberty and property of others. So, it is wrong for me to just walk up to somebody in the street and kill them, because I am taking away their right to their own life. However, if I attempted to kill someone and failed, they have a right to defend their own life with maximum possible force. There is nothing more precious to me then my own life, so I will defend it to the maximum extent possible, and if that means killing a repeat offender criminal dipshit, then so be it, I won't be going to the morgue in a body bag.