Here's an insightful way to consider the Trayvon Martin-George Zimmerman encounter, which led to the tragic killing of the teenager. Let the situation be the same in all respects except one.
Assume Zimmerman was a 6 foot, 5 inch, 250 pounds of solid muscle man who walked with attitude instead of the small-in-stature guy he actually is.
Would the fight still have take place in this situation? I think not.
Trayvon would have taken one look at the guy and turned around and returned to the condo where his father was staying. People don't voluntarily enter fights when the odds are stacked heavily against them.
I believe this fight took place because when Trayvon realized who was following him, he was sure he could beat him and that's exactly what he was doing when Zimmerman drew his gun and shot him.
I believe this shows that Trayvon chose to start the fight which resulted in his being killed. The responsibility for this tragedy is not just Zimmerman's.