META: Magic in Fenspace

[Ace Dreamer]

Although there is a small moral question that invokes.

A mage and a mundane have an argument. The mage decides the mundane's not getting it and needs to have some understanding shot into them. If a mage fires off a non-lethal spell that'll knock out a mundane like a punch to the face, and the mundane fires back with a decent handgun that'll probably kill the mage..... has the mundane used excessive force to defend themselves?

If someone aims what I believe is a loaded gun at me, and I'm sitting behind the wheel of a car, am I entitled to try and run them down?  What if it's a baseball bat?  A clenched fist?
If the mage was a martial artist who launched a KO blow at a non-martial artist, is the other entitled to pull out a gun and shoot them?
Or, does the mundane shout "Witness!" and their mobile goes into full record-and-streaming mode, with all sensors including magical ones, and the mage knows the whole situation is likely to appear in their court case?
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"It is the business of the future to be dangerous" - Hawkwind