Taking the whole thing into account, taking as given America’s history of racial tension, thus taking as given the practical inevitability of “racial profiling”, I think the root cause of Trayvon Martin’s death was that George Zimmerman was allowed to carry a pistol.
Racial profiling works both ways, I don’t believe that Zimmerman would have ever dared get out of his car and accost a young, black male in a hoody even to comment the weather or to ask for a light, if he hadn’t been armed.
The more racist he was, the more frightened he would have been and the less willing he would have been to approach Martin. Without a gun he would have waited, safely locked in his car, for the police to arrive.
So for me it is clear: letting people carry pistols in the street caused the death of Trayvon Martin as it is the cause of death of thousands of Americans, of every possible color, every year.