From an emotional standpoint, this doesn’t make Zimmerman look good at all. However, this isn’t about emotions. It’s about whether this affects the legal case.

From a legal standpoint, this would ordinarily be considered character evidence and character evidence is generally inadmissible (along the lines of FRE Rule 404). There are exceptions to the rule - such as when the defense introduces character evidence, which is when the prosecution could introduce this kind of evidence to rebut the defense claims. The defense would have to open the door to character evidence before the prosecution could rebut. The prosecution couldn’t use this as proof of Zimmerman’s tendencies or racist/hate-filled past.

However, under a federal hate crime charge - such as under 18 USC 249, prosecutors would have to show that the victim was targeted because of their race, color, religion, or national origin. That would require statements by the defendant showing that he targeted the victim on the basis of his or her race, color, religion, or national origin or that he expressed views towards the group to which the victim belonged (hated African Americans, gays, Jews, etc.)

So, this might not be admissible in the state murder case against Zimmerman, but it could form the basis of a federal case that Zimmerman violated Martin’s civil rights - that he hated and targeted minority groups.