If that's the case, they need to change the stand your ground law.
Without stand-your-ground, Zimmerman would have to flee. But being on the ground underneath Martin, he had no chance to flee, so stand-your-ground does not apply, it was simple self-defense.
You just don't get it, do you? That's NOT a "stand your ground law." It's the regular, ordinary old law on self-defense. What happened to my friend happened in the nineties... long before anyone had ever conceived of a "stand your ground" law!
See, the word "defense" in "self-defense" has a meaning. So long as you are defending against an attack or threat, you can claim self-defense. As soon as you begin attacking (note the difference between that word and "defense"), especially after gaining the advantage (let's say, to make up a random scenario, you were sitting on top of someone, slamming his head into the ground while he screamed for help), you have become the aggressor and the new victim can now legally defend himself from you.
It's a simple and logical concept that has been part of common law for centuries...