It's not nonsense. It was my first reaction to that line - and I'm not a knee-jerk "cry racism" guy. More often than not when race has been discussed on this board, I'll chime in saying it's an overreaction or something.
But I've heard guys talk like that, and sound exactly like GZ did. I'm not saying that it proves definitively that he was a racist, or that this was a racially motivated crime - but it sounded racist to me. His tone & words were a frustration borne in part of racism. He's not following Trayvon because he's a robber - he's following him because he's black.
Interesting take. He couldn't possibly be following an unknown person in a neighborhood that had been victimized by crime in the recent past, he can only be saying a special code that you've "heard guys talking like"?