That's the thing though, isn't it? The law needs to work for both sides involved. As was argued in the case, Zimmerman claimed he left the car to look at a street sign, in a neighborhood he'd lived in for four years and was the Neighborhood Watch leader for. It's not beyond the realms of possibility I suppose, but strikes me as unlikely. Once again, he may have said this purely because he knew the legal eggshells he was walking on, and there's nothing wrong, in essence, with following a suspicious character.
However, the chances are a campaign would have more impact than a riot, even if it achieves 'nothing' with regards to changing the law itself. I agree that the law needs to support people who defend their own neighborhoods, I come from a country that cannot even make up its mind properly how to react to a home intrusion, but it also needs to stress that 'playing the hero' and trying to confront a suspect face-face should only be done if a crime is actually seen to be taken place and/or people are in immediate danger, not that one is assumed about to.
Maybe Zimmermans' comment that 'nothing ever gets done about it' to the Police before he pursued Martin is a more telling comment in the case than it has been taken as, it's often used here as a reason for vigilante action, the -not always unfounded- assumption that if the matter is left to the Police, it will have no long term impact on the situation.