there are certain times it may not be justified but if someone was shooting to kill you and you were shooting at non fatal areas of the body to incapacitate that individual then your violence is definitely more justified than the person shooting to kill
i agree partially because lets face it if you were going to court for shooting a cop non-fatally and you tried to classify it as "self defense" you are more likely to get charge with attempted murder than shooting someone else under the same circumstances.
thats the thing lets say someone IS trying to kill you there are the non-violent methods of stopping that personalthough i agree partially with your arguement "self-defense" there are extremely effective non-violent methods to subduing your attacker