Don't think it's as cut and dried as either side makes it. Putting aside the fucked up laws around this shit in Florida (and the US in general), imo Martin shouldn't have reacted to Zimmerman's harassment the way he did (and yeah, if some random asshole came up to me while I was walking home and started questioning me about whether I was a criminal, I'd consider it harassment), unless I've got the chain of events wrong and Zimmerman actually initiated the physical side of the altercation, Martin should have just blown him off and walked away.
The flip side of the situation being that what Zimmerman was doing is, in my line of thought, way out of line. If he wants to wander his neighborhood keeping an eye out for suspicious activity, whatever, that's his right, but he crossed the line when he walked up to Martin and initiated contact, especially after emergency services specifically told him not to. So Zimmerman bears the blame for creating the whole fucked up situation, and Martin bears the blame for escalating it to physical violence.
It was a shitty confluence of shitty circumstances from two people who obviously just didn't know how to deal with the world very well. if you want to place the blame on one party more than the other, then that definitely goes to Zimmerman, I mean what the fuck did he think would happen? That everyone he suspected of being a criminal would play into his wannabe-cop power fantasies? So while the blame in the end of the day lies with Zimmerman, that doesn't really equate with what he did being cold-blooded murder.
Delusion met aggression, one of them had a gun, the other died. That's what it comes down to.