Zimmerman's defense rested on one thing: self-defense. Society has laws in place that say murder is okay when you are defending yourself. And it's not just murder. The whole job of lawyers is to make excuses. We rationalize crimes all the time. Examples:
Lying is not wrong if used in the right occasion. How does this new haircut make me look? Truth: Terrible. Answer: Oh, it's so cute! We justify deceit if we think the consequence of truth is bad.
Theft is not wrong if it's used against the right people. Isn't that why people love Robin Hood? He steals from the rich? Isn't that why people pirate software? Because wealthy corporations are the victims? We justify larceny if we think the offended party is bad.
Murder is not wrong if you can justify it. We live in a country that kills babies in the womb by the millions. But we don't want to bring a child into this kind of world, we say. But we aren't ready to be parents, we say. But the child is unwanted, we say. We justify murder if we think our life is in danger, or if our life is simply inconvenienced.
God gave man reason, and man uses that reason to find excuses for its choice to rebel against God (i.e. sin). The Zimmerman verdict doesn't just illustrate we have a broken legal system. The verdict doesn't just illustrate we have a broken society and culture. The verdict mainly illustrates this: that we have a broken relationship with God. Of all the things that should infuriate us, that is the thing.