Not sure what yall are debating about but if some dude were to pull a knife on me, and threaten my life, regardless of the pocket change, I would probably shoot him. Like I would tell him to leave first, and that if he were to approach me, I would consider it him trying to assault me. I'm sure I have some law stuff wrong but anyways.
I'm sure other countries have bizarre laws (or rather, ones that seem bizarre to us) concerning assailant's rights and such. Like, I think I've heard that in Italy even if someone is breaking into your home if you shoot him it's considered attempted murder and you will see trial for defending your "castle". It might even be the case if he physically assaults you, something to the tune of "escalating the situation". In other words, the only way you can use a gun in self defense is if he uses a gun to attack. Could be hearsay, I don't remember where or from whom I got it.
I'm more on the doctrine that if you are mugging me or invading my home, you are doing so under the condition to do me harm. Burglary is one thing, robbery is another. The only reason you would force your way into my home while I'm there is to do me harm, and I will respond with violence.
Of course, though, having a guy pull a knife out in an alley on you and the first thing you do is reach for a gun you'll be stabbed before you can even get it close to being on target. The distance required for draw and shoot is a lot bigger than you'd expect. In that situation it would be better to cooperate unless you are trained in hand-to-hand and willing to risk your life and safety over a wallet and maybe a watch.
If you are cooperating, then when the guy has your valuables and is fleeing you kind of have no right to shoot him in the back since he's no longer a threat to you. It's a tough call.