I think the Zimmerman family has felt at least as early as the APC was issued that this case was less about the law and more about something else (skipping grand jury was probably their first indication). Are they justified in that thinking? I dunno, but I can understand the position given how the case was portrayed in the media early on (big white man killing black child and inept/racist police department letting him go, SYG law the bane of everything evil, etc.).
I agree that RZ should stick with publicizing the facts surrounding the legal case until that part is decided. Whatever else he believes may be occurring is mostly irrelevant until that is resolved and bringing forth motives for GZ's prosecution now doesn't help their cause unless there is a smoking gun of sorts. I would guess he knows more about the prosecution's case and the position the defense is in more than anyone here, but from a pure publicity stand point, I don't think these twitter comments are a good move.