@urangutan,
Not sure what you mean by that, but its a good example of the murky area of such an ethical issue. And for reference, if an undercover cop aims a gun at me he's still putting himself at risk for lethal means of defending against imminent danger like anyone else
To me (like most ethical issues),
preemptive self-defense has its cases that one might judge clearly-justified, clearly-unjustified and those which could go either way. Like a scale traversed, absolutes are exceedingly rare.
As I illustrated with the silly example a few posts back, basing culpable responsibility on
perception is fine, but only to a point. But then again, one can't wait until a bullet's in clear-flight to act. Both extremes are absurd, almost as absurd as "...the perceiver is not responsible for over-reaction".
Another large factor in this equation is the role cultural standards play. Although I'm not sure such a thing would relegate the issue necessarily since reaction to perceived danger isn't contingent on social construct.
Good discussion