Ah but that would imply that Zimmerman was still following Martin when the attack happened. Apparently Zimmerman had stopped at the entrance to the dog path, and Martin moved all the way down the street to his father's townhome, then returned and confronted Zimmerman. So there was no ambush. And ambushing someone who is following you when they haven't engaged in physical violence against you probably makes you the aggressor as well, which I agree, a little weird.
However, I could see the jury finding Zimmerman's actions as mitigating circumstances that prevent him from total exoneration, hence why I think manslaughter or negligent homicide might be better charges to find him guilty of.
The problem is determining to what extent Zimmerman's actions justified Martin attacking him, if at all. And that, of course, seems to boil down to perspective. I do think Zimmerman was a retarded mall cop wannabe who was far over reaching what he should have been doing in terms of self policing his neighborhood, but if Martin initiated the physical violence after escaping Zimmerman for a period of time, from the legal point of view, all that stuff becomes sort of moot.
From an non legal standpoint, I completely agree with you, these should all be mitigating circumstances, but when thinking about it like a juror and from the instructions jurors are given and the context of the law, I'm just not sure any of these other factors (Zimmerman racially profiling, Zimmerman intiating the original event by being basically a neighborhood vigilante, Zimmerman listening or not listening to the 911 operator, etc) are going to have any impact whatsoever.
Of course since its a jury trial, who really knows what could be considered an important factor to any particular juror. They could very well consider Zimmerman's actions to be the cause of the killing and find him guilty of second degree murder. I just don't think its likely at this point.