Ok, correction: I think ethics is akin to medicine or nutrition. It really helps if you consistently apply it everywhere in order to prevent extreme scenarios.

Ok, correction: I think ethics is akin to medicine or nutrition. It really helps if you consistently apply it everywhere in order to prevent extreme scenarios. And when they occur, and ethics do not help, it's not a failure of ethics, but your failure to use ethics to avoid situation when someone actually threatens you with a nuke. To say that general rule "do not use violence" does not work in extreme cases, is like saying that medicine is useless because it cannot make you perfectly healthy when you have a heart attack. But it is useful because it helps you to prevent heart attack in the first place. And if you ignored the knowledge and now having a heart attack, then how can you say that it is useless?