re: "Didn't look life threatening"
It WASN'T life threatening - which was lucky for George. But he had no way of knowing whether Martin was going to stop. And only a fool would wait until the concrete DID cause a life threatening injury before defending himself from it. Do you agree with that? That only a fool would let it continue?
A few hits of the head against concrete will kill a person, clo. In fact, ONE can. Dozens of people die that way every winter.
I'm not sure what you think a concussion is supposed to LOOK like. It's a brain injury, after all, not a skin injury. It happens to football players even when they have helmets protecting themselves.
I can tell you that any one of those bruises on Zimmerman's head COULD have had a corresponding concussion.
Finally...
re: That said, if Trayvon punched me, my first response would be to react & hit back. If he knocked me to the ground, I would roll."
That may just be the dumbest thing I've ever seen you write. But, maybe I'm the naive one here. You'll tell me with an honest response to this question:
Have you EVER had your nose broken by a punch to the face?
If not, clo, I respectfully assert that you have no idea how you would react.
There are countless boxing matches that ended seconds after they began, when one of the TRAINED ATHLETES immediately took a blow to the face and was then GONE. DOWN. OUT. It's part of the reason the sport has such a bad reputation. People like you cannot even relate to what such a punch can do, and think that the fight was fake. (Okay, I'll admit that it doesn't help that some of them ARE fake!)
Yet yet you know what you would do if a football player slugged you in the face! You display un-be-lie-vable arrogance. Unless it has happened to you, I mean!
Watch the following and learn something.
http://www.youtube.com/watch?v=F_mChJtTAYA
This next one is a longer video, but the fight starts at 4'32" into the video. You may wish to zip forward to it. Don't be late. The fight ends at 4'34".
http://www.youtube.com/watch?v=piFrcZUHeOk&feature=related
Another? This fight also lasts two seconds.
http://www.youtube.com/watch?v=IZFtUJzV8xk&feature=related
There are a TON of them. But you'll probably think they were staged, so here's a National Geographic piece about the power of ONE punch:
http://www.youtube.com/watch?v=sfnGkV6qmTw
But you know you'd roll if you were hit in the face with nose-breaking force. Please do elaborate.