Are you saying that it is reasonable, socially acceptable, or legal to physically assault someone who you believe to be following you?
All of the noise about Martin rightfully availing himself of the Stand Your Ground law is just that. Unless Zimmerman was waving his gun and yelling to Martin how he was going to shoot him, the teen punching him in the nose and bashing his head against a curb would not constitute a reasonable reaction.
It appears to me that there is evidence that Martin attacked Zimmerman, broke his nose and bashed his head, but it could be proven otherwise.
One can argue that the degree of assault didn't justify being killed, but as I have told my sons, the minute they resort to violence at any level they are opening a very wide door. Anything can and does happen and it doesn't matter how far the instigator wanted to take things. You start a fight and you don't ever know how it will end.
If "all" you do is break someone's nose with a punch, your an idiot if you think that they are limited to that level of violence in retaliation.
Outside of self-defense, once someone uses or seriously threatens violence, they have no right to bitch about what sort of response they receive. It's very easy to avoid the wrath of someone who responds to threats or violence with insane rage.