People are just pissed because it shows, quite blatantly, that racism still exists.
link - that's why people are angry. The American justice system is based on the words of the whites because they've got مزید power. For instance, blacks are convicted at a much higher rate than whites یا other minorities. As a result, there's no real justice in the justice system. I'm not suggesting all whites in the system are racist, few of them outwardly are, but the racism is still ingrained in American society and minorities are still picked on. That's what pisses people off, including me.
EDIT: And yes, the verdict of not guilty was based on lack of evidence, but try and tell me that the jury and the country wouldn't feel مزید sympathy for Trayvon and his family if he was white. Try and look at the numbers and tell me non-blacks aren't let off as "not guilty" مزید than blacks.
ترمیم 2: It's also a big deal because Zimmerman called 911 on Trayvon and they told him to stay in his car. Zimmerman got out and shot the kid instead. For that reason he should definitely have been found guilty of murder. Trayvon wasn't a threat to him.
"In this country American means white. Everybody else has to hyphenate."
-Toni Morrison