Your logic is flawed. He didn't intend in provoking an altercation while following TradeMark. His intent was to assure another burglary was not committed. He had no idea that Martin would eventually assault him and have him getting his head smashed against the ground. He did what he felt necessary to preserve his life. That's not murder it's self defense.
I wonder what Trayvon Martin was thinking leading up to the confrontation?
He's walking through a neighbourhood with, from we understand, no ill intent. A man follows him for awhile in a vehicle, then gets out and starts following while on the phone. At no point (as I understand it) does this man following him say anything or identify himself (why didn't he? If his goal was to prevent a burglary, wouldn't it have made sense to say "Hey, I'm from the neighbourhood watch. What are you doing here?" I'm coming back to this later).
From Martin's perspective, he's walking through a neighbourhood and and a stranger starts following him. That clearly scared him, that's why he confronted Zimmerman.
But he's dead, because Zimmerman killed him, so we will never get to hear Martin's side of the story.
And I want to address this communication issue more. Was Zimmerman's goal to catch the kid in the act of breaking into a house? Doesn't it make a lot more sense to announce yourself as outlined above? The whole "fear for your life" thing may play a role in not wanting to anger this potential criminal, but the question then is what Zimmerman intended if Martin broke into a house. Or was he hoping to simply dissuade any criminal thoughts through his presence? In which case, if he thought this kid was a criminal, why would he not expect confrontation?