> Not in all cases, but criminal acts are capable of cancelling each other out. Self defense is the archetypical example.
Of course the law states an exception for such cases, and usually includes(at least as far as nordic countries are concerned, which of course has no relation to the law in US, but it's something I am more familiar with) a statement which requires/encourages "least required force" too. So you can't just beat someone up in the name of "self defense".
The public opinion itself, as far as it seems to be, is that whatever is good as long as it's in the interest of US, be it morally justified or not. For example violating the privacy of foreign internet users is all good and somehow justified because "it keeps US citizens safe". Yeah right.
In the U.S. self-defense requires a reasonable belief that one's safety is at risk. Parodoxically, this operates the opposite way that Nordic countries apparently do: here, you are less likely to get in trouble for using extreme force (eg. shooting someone in the head) than trying to use less extreme force (eg. breaking their wrist and disarming them), because the extreme reaction shows that you were under a clear and present danger and had to act quickly, while a more measured response indicates that you had time to think and consider your actions, and if you had time to think you probably had time to do things within the existing legal framework like escape or call the police. (All this, of course, is subject to other circumstances: if you break into someone's house and shoot them in the head, it's significantly different from if they break into your house and you shoot them in the head.)
The interesting thing is that the U.S. system seems to function from within the head of the accused: given the situation as you perceived it, did you believe you had no other options other than deadly force on your attacker? While your description of the Nordic system indicates that it functions from a more dispassionate, third-party observer's perspective.
You're thinking of a different concept I think, i.e. when is it allowable to use deadly force at all.
If you fear for your life or are in danger of serious bodily harm you normally have the right to use deadly force (sometimes you must also have no way to escape, but let's just assume you're clear to use deadly force). Once you're in that situation it's advantageous to actually use that force. You wouldn't try to shoot someone in a hard-to-hit area like their knee or shoulder because as you say, if you had the time or perceived the danger to be low enough to line up for a shot like that, you were probably not in a situation so extreme that would warrant use of deadly force. It would be legally more defensible to go all Mozambique drill on somebody on put two in the chest and one in the head.
However, given that you are in the situation where you must defend yourself, but where deadly force would not be allowed, proportional response is usually still the operative concept.
If someone comes at you with a bat and you manage to disarm them that doesn't give you carte blanche in the U.S. to beat the attacker to within an inch of their life.
Of course the law states an exception for such cases, and usually includes(at least as far as nordic countries are concerned, which of course has no relation to the law in US, but it's something I am more familiar with) a statement which requires/encourages "least required force" too. So you can't just beat someone up in the name of "self defense".
The public opinion itself, as far as it seems to be, is that whatever is good as long as it's in the interest of US, be it morally justified or not. For example violating the privacy of foreign internet users is all good and somehow justified because "it keeps US citizens safe". Yeah right.