When the OJ decision was released, I was shocked that every one of my African-American friends thought it was a just decision. The right decision. They actually thought he was innocent. I know of no white persons who sided with the OJ decision. The opinions about the OJ decision were split down racial lines much more than the MB decision is.
Too many people base the decision of whether someone is guilty or innocent on whether they have the same skin color or not. While it's possibly excusable or at least understandable as an initial knee-jerk reaction it's less justifiable when there has been an investigation and more facts based on evidence have come out.
We need to separate the reality of what happened from the claims being made about what happened. Some people just can't do that. It shows how danerous the "first lies" are - things that are initially reported get repeated over and over and some accept them as fact even if they are debunked.
The OJ case is rather unique because it was a very public and very botched prosecution. I don't believe black people really believed he was innocent, I think they didn't want him found guilty because he was a black icon.