From what I’ve read, the judge may have been correct to keep out the stuff about Martin’s prior conduct. While, according to the Florida Rules of Evidence, the character of an alleged victim may be offered by the accused, Rule 405 states that “When evidence of the character of a person or of a trait of that person’s character is admissible, proof may be made by testimony about that person’s reputation.” So, while Zimmerman could put up witnesses to testify that Martin had a reputation for starting fights, the Florida Rules of Evidence seem to bar evidence about specific prior incidents.
The testimony of Witness Eight suggests that she didn't seem surprised at the notion of TM starting a fight with GZ. Could MOM/West pursue that further if they call her back to the stand? It would seem that if TM was in the habit of getting into fights with strangers, it would be at least plausible that he would have instigated the fight in this case, which should in and of itself imply reasonable doubt.