What if, Martin did attack Zimmerman first as was alleged and he was beating him, it is reasonable that someone could be scared that their life is in danger and react the way Zimmerman did.
This is where the law needs to be fleshed out more, IMO. The evidence indicates GZ initiated the entire thing by profiling and following TM. No doubt, he feared for his life when the victim turned the tables on him. However, many don't believe the aggressor should be allowed to shoot people, at the point he feels threatened and then walk away free. This is what most of the commotion is about.
How do we flesh it out? If Zimmerman had started walking back to his truck as was stated then he was no longer the aggressor and Martin had nothing to defend himself from. You can change the law to require a duty to retreat and Martin would have still been in the wrong in that situation because he did not retreat.
You can make it unlawful to follow someone, but that opens a whole different can of worms, what happens when someone just happens to be walking the same direction as another person, but the person thinking they are being followed feels threatened, does that justify attacking the person following?
We do not know what really happened and all we have is the evidence and testimony that was presented at the trial. The jury found him not guilty, that doesn't mean he is innocent, but it means that there was reasonable doubt when it came to the charges against him. Any reasonable person looking at the evidence objectively should come to the same conclusion when it came to those charges.