I don't know if this was a racial issue or a "person don't belong in here parts issue" which is apply in a lot of places as there places "outsiders" just don't usually belong.
There was probable cause to ask the question. What escalated the question to a physical altercation is the question.
There wasn't probable cause unless someone with Martin's description was seen breaking into dwellings. Sanford's 30% black. This isn't The Hamptons. Young Black Males aren't out of the ordinary there. There may or may not be reasonable suspicion for a cop to stop and question this person. There is no cause for George Zimmerman to himself detain Martin.
Zimmerman could have talked to him, but if he was aggressive and had bad intentions (possible), Martin had full reason to defend himself. If Zimmerman was the aggressor and got more than he bargained for in response, then he has 'imperfect' self defense at best which is usually a one way ticket to getting dinged for manslaughter. The only way I see Zimmerman possibly beating a manslaughter ding is if he said simply he wanted to talk to him and Martin charged and attacked him. Based on the limited facts I've seen, I don't see that.
As much as I effing despise the race pimps, they may be right on this one thing.