A priest who accidentally kills someone must step down as a priest, though sometimes, as a matter of economia , he will be reinstated. To shed blood is a very serious thing. To take a stand of nonviolence no matter what is fine if you are a monastic and have a different set of obligations and no children. It may well be quite different if you have a set of concrete obligations to the aged and to children. I do not believe there is one answer to this question.
Different people have different callings.
If you are willing to die to make such a statement, then do so. However, those who feel no such calling have no such obligation. I would rather stand before the Dread Judgement seat having killed someone who attempted to harm my little sister or my priest's children or for that matter any child than to have allowed it to happen. If I could stop the person without killing them, I would. If I had to take an even small chance that my action would not stop him if I used something less than deadly force, I would not take the chance.