This is particularly germane in light of the recent Trayvon Martin case, where an unarmed athletic youth was able to beat an overweight CHL carrier practically unconscious with his bare hands.Uhh...I don't know how you can say that an "unarmed" attacker does not constitute a threat to your life. This is dangerous advice at best.
The fact that a person is confronted with any "attacker" is in fact a threat to their life. The victim will very likely not have the opportunity to frisk their "attacker" beforehand to determine whether they are armed, or to interrogate them to determine whether their "attacker" intends to: pummel them to death, throw them in front of a bus, to strangle them to death for sport, or to "merely" cripple them for life. When one is attacked, one must do whatever they are able to defend themselves.
I am a Texas commissioned security officer (not an LEO!), and our training includes sections on the definition and use of deadly force. In Texas, "deadly force" constitutes anything that can potentially be either fatal or cause permanent and/or severe injury. Any attack which could potentially break bones or crack a skull is considered deadly force by Texas law. Hence, most women can reasonably use deadly force in response to an empty hand attack by most healthy males just given the typical disparity in physical power between men and women. So too could a man threatened by multiple attackers or by an attacker demonstrating a gross physical advantage such as expertise in the martial arts.
No, that's not carte blanche to gun down every bigger guy you see on the street or take out a dojo full of teens, it just means that an attacker doesn't have to produce a weapon to be considered dangerous. Just try not to get in situations where it might be necessary.