There is no question that the night of Martin's death, there were a large number of bad decisions made and poor judgement exercised by both parties resulting in a tragic outcome.
Regardless of personal opinion or belief, trials are not meant to be decided on public opinion but rather, evidence. The jury was not presented evidence pointing to guilt beyond a reasonable doubt. It would appear that they decided GZ not guilty because the prosecution didn't present a strong enough case.
If public opinion were to drive the process, then we would not need trials...the media could decide for us and we could just release the defendant to the crowds to administer the punishment. It may "feel" good, but I doubt any of us would want to have our futures decided in that manner.