obligation, legal presumption of innocence, backup
If I am walking down the street and someone looks like they are going to ask for cash, do I need to become a warrior? nope.I think there is a confusion between being armed and proficient with your weapon of choice and being a warrior. Two different things, not all warriors had any training at all, and not all highly skilled marksmen are warriors. Look at Audie Murphy, he hardly looked like a warrior and I doubt he received any more training than the typical service man but he seemed to do ok. I would assume he got his warrior mindset in the middle of the combat, he realized it was "him or them" and voila a warrior was born instantly on the battlefield.
If someone wants to kill me, and I have to react now to save my son's life. I need to become a warrior now. It becomes a mindset of ultimate survival, and "anything goes" without losing ones' cool.