OK, let's rephrase and say that it's an apparent fact that Martin attacked Zimmerman.
The assumption of the truth of that fact is the basis of the presumption of innocence which is at the heart of our legal system.
If Zimmerman goes to trial, a self-defense argument will be presented. It will be up to the jury to decide if there is sufficient evidence to contradict the defense's claims of self-defense. That will be the only "genuine proof" you will ever get. So, in reality, your snide request is really nothing more than a statement of the obvious: that a trial has not occurred yet.
The truth of Zimmerman's claim that Martin attacked him, I guess, at least as far as the court is concerned, will be decided by the jury in that trial.
To reiterate, the "genuine proof" you demand is a phantom which will cannot fully materialize until the actual trial occurs. So you can sit there and smugly make a demand which is currently impossible to satisfy. Congratulations.
Currently, however, it is clear that Zimmerman claims he was attacked by Martin. That testimony stands unrefuted. Furthermore, the additional evidence we have access to, such as injuries sustained during the struggle, also seem to support that conclusion.
Conversely, I have not seen anyone, including the prosecution, present any evidence that Zimmerman attacked Martin. So while you can feel confident that no one can realistically meet your impossible standard of "genuine proof" regarding Martin initiating the attack, it really serves no useful purpose, other than to expose your obviously disruptive intent.
We have a biased media and an overreaching prosecution to deal with. If you choose adopt their point of view, that is your business, but don't pretend to be some unbiased seeker of "genuine proof", because that is obviously not what you are after.
It can't and won't appear at trial either. There is no independent reliable, credible and trustworthy on-scene eyewitness, no video. The issue cannot be resolved to the standard of proof that wtc911 demands.
No matter, that's not how the law works, nor is it how people resolve uncertainty in serious issues. There is other evidence, plenty of it.