You left out the "fact" that Trayvon laid in the morgue for three days with a "John Doe" tag on his toe in your list of irrelevant facts.
so every single eyewitness seeing this happen in the grass is "irrelevant", even though zimmerman says it happened on the sidewalk?
so suppose your son gets killed. the killer says to you, the father, "sorry man, i was fearing for my life! he punched me in the nose (from behind) and then slammed my head on the sidewalk!"
you then talk to the eyewitnesses, and every last one of them says the short scuffle happened in the grass.
you still gonna accept your son's killer at his word, even knowing he has a long history of violence, aggression, and losing his temper?
i bet you don't.