Also, what sort of information are some of you basing your idea that he did in fact to continue to follow and confront Martin?
Well, had Zimmerman not followed and confronted Martin, Martin would still be alive... right?
Further, the 911 operator repeatedly kept asking Zimmerman if he was following Martin. Zimmerman kept telling the operator that he was, that he had seen Martin running away from him, and that he was going to see what was going on with the situation. The operator kept telling him that it was not necessary to pursue Martin.
Neither of these should play into how the case is handled.
Indeed, you are right. Race, nor the associations we often make about other people's skin color, should not play a role in the incident. But there's a difference between what should or should not happen, and what actually happened. The role of race goes to your question:
Since when do you need a gun to be threatening?
Indeed, you don't need to have a gun. But in this case, Martin never exhibited any suspicious behavior that warranted Zimmerman's 911 call nor Zimmerman's suspicions. While people are bogged down with the details of the confrontation, no one asks "what was so suspicious about Martin that made Zimmerman feel that he needed to call the police and to follow him in the first place."
Sure, as the facts suggest (vaguely), Martin began to run away from Zimmerman. Here, the general public can ask (and Zimmerman certainly did): "well if he hadn't done anything wrong, why did he run?" But there's another possible answer to Martin's running away: If you're being followed at night by some stranger, isn't possible to feel a sense of danger? A sensible thing to do after you feel endangered is to run, right?
For Zimmerman, what was so suspicious about Martin? Had Martin been older, white, and been wearing a Harvard sweater, would Zimmerman have called the police in the first place? My feeling is that no, he wouldn't have. But this all begs the question: how did Martin's skin color and wardrobe contribute to Zimmerman's feeling that Martin posed a threat. Does a certain skin color pose a threat?
So yes, race, in a perfect world, shouldn't matter. But the fact that there's a black kid dead, and given the circumstances, all of this suggests to me that race, that night, did matter.
This is why this case is so crazy.