You're conflating the nickname of the law with its actual intent...that being you have the right to defend yourself with deadly force anywhere it is legal for you to be.
And that's the way it SHOULD be.
The police dispatcher has no more business telling you not to confront someone than they have telling you not to defend yourself from an assault ... it just makes their lives a lot simpler if you act in the authorities best interest.
It was legal for Trayvon to be there too and I could make a case that George Zimmerman was stalking Trayvon that night.