Joe Oliver, an African-American friend of George Zimmerman, tells us that he doesn't believe Zimmerman said "coons" and even if he did "coons" is not actually a racially offensive term:
That's a term I listened to over and over on there and to me, it's a matter of interpretation of whether he's saying 'coon' or 'goon.' There are a lot of parts of this country where people proudly call themselves 'coon asses,' in Louisiana in particular.
One reason why having a black friend(s) says little about your identity is that black friends are human friends, and thus subject to all the array of ignorances that all other human friends are subject to.
As ThinkProgress reports "coon ass" is most certainly an offensive term. The fact that some people use it proudly, only shows that some people have a sense of irony and an understanding of context . Toby Kieth's White Trash With Money is ironic. Me going calling a white dude on the street I'm arguing with "white trash" is not.
These subtle differences are important, and nothing about being "black" guarantees you will be nimble enough to understand them. I'm sure I can find an Asian-American, somewhere, who will assure me that I may use chink at my leisure and not expect an ass-kicking to follow. But I think it best to decline.