ChuckS, there's a thread in Tactics & Training you can check out that covers some of the logistical issues.
As far as legal issues, the author is correct.
Is criminal activity AND attack both necessary to invoke applicability?
No, but the law allows intervention in the case of a forcible
felony. Jaywalking or trespassing don't allow for the use of lethal force.
I do know "fisticuffs" can be deadly. Does it require a trial and jury to define what a reasonable person response to fisticuffs is in every case?
I have a friend who's an expert in several martial arts. He's testified in a couple of lethal force cases that yes, fisticuffs can be deadly, and that lethal force can be a rightful defense in some cases.
It'll be different from situation to situation. An NFL linebacker probably won't be as threatened by a guy my size swinging his fists, but if the situation were reversed, I'd probably have a valid argument that lethal force was justified.
Nonetheless, we'd need a jury to determine that. Homicide, justified or not, always merits scrutiny.