The American comment was admittedly flippant, but the point remains that you cannot construct morality on edge cases.

Violence is abhorrent. Frequency is relevant because one can base one's life and actions on principles of nonviolence, and deal with such extreme situations in the unlikely event they ever come up.

It's a dumb playground question, like would I cheat on my wife if $FAMOUS_HOTTIE came on to me.

One can live one's life by not being violent, by not working in violent industries, by not owning weapons, by seeking and promoting solutions that do not involve violence in one's community and national politics. This is a morally correct life.

Sure, one day, someone might try and kill my child. I hope it never happens, and I hope that situation could be resolved without anyone dying.

But say, somewhere in this long tail, I killed to defend, I don't believe that would invalidate how I've lived the rest of my life.

Only extremists create their principles from extreme cases.