That isn't true, though - there is actually no known evidence either way to say which one of the two people was the attacker. During Gilbreath's testimony at the bond hearing, he stated that they had no evidence at all of which one of them threw the first punch. So to say that "TM responded to the provocation with aggression" is speculation only.
I also disagree that "a provocative act is not the same as an agressive act," in that it that makes the false assumption that provocation can't be physical (it can), or that aggression is ONLY physical (it's not). Besides, it has been discussed here quite frequently that SYG does not require that physical assault or injury be experienced in order to feel threatened and in fear of one's life. Confrontation by an armed assailant could very well make one fear for one's life, I think.
Based on the evidence that is available thus far, I would say that the prosecutor is responding to the fact that there are numerous inconsistencies with the timing and content of George Zimmerman's story, questionable intent on his part, contradictory information from witnesses, etc. Besides, wouldn't pressing charges without proper evidence and good faith in their case make the prosecutor subject to serious repercussions and possible disbarment? (That last question is a real question on my part - the prosecution can NOT knowingly bring a frivolous charge, or they open themselves up to numerous issues, right? Does anyone know more about that? Info is appreciated!)