For example an unarmed neighbor coming to take back what he feels is his property, even if he's mistaken. A brother come to take some item of Dad's he feels should have gone to him after the funeral? These things happen all the time, and they put PROPERTY at risk.
Both of those things have the potential to NOT be crimes.
Again, we are talking about clear criminal acts against property in one's immediate surroundings.
Someone on the roof of your building stealing copper from the air conditioner, to keep the example here, are clearly not going to turn out to be an "accident" or a "misunderstanding".
Of course judgement should play a role in this, no one is saying otherwise, but your examples do not address a real, immediate, clear criminal act in the presence of the property owner.
THAT is what we are talking about here, not killing some guy that stole your bicycle 20 years ago.
Let me put it this way, if the law permitted you to shoot an accountant you caught cooking the books, would you?
No, because that is not an immediate, personal space type of crime. It's simply not the same thing this thread is talking about.
If it were the case where somehow if I caught this accountant and it would result in an IMMEDIATE return of my property, and I believed that there was NO OTHER WAY to get said property back then yes, perhaps force would be appropriate. It's that immediacy, and the lack of alternatives that brings this into play. A stranger that I don't know, stealing my tools, is hampering my ability to make a living potentially and I might have no alternatives to getting my tools back. To me that's where the line comes in. If faced with no other means of keeping what is mine, I believe there is a moral allowance for the use of force in am immediate circumstance, and that's what the law says as well.
And I'm not sure why you keep wanting to separate the legal from the moral side of this. Most laws come into existence because of some morality behind them so they are forever connected in some way.