Holy crap, man! That wasn't the question. Would it be okay to follow him and ask him what he was doing if he was peering in windows and checking car doors?
Not if you have to shoot him. If you're able to deal with the situation appropriately, then sure. If not, call the cops and let the professionals handle it.
I have no problem with Zimmerman calling the cops. I have no problem with Zimmerman following him (in his car) to see where he is going until the cops arrive. What I have a problem with, is Zimmerman approaching him if his only way to defend himself is to blow the kid's brains out. If you're fit and can handle yourself, fine. If you get your *** kicked, you gave it a great effort and hopefully the cops get there before too long.
And if you want to be a neighborhood watch, and confront people that you don't know, then you had better be able to defend yourself without taking their life. Either buy a tazer, buy some pepper spray, hit the gym, bring a friend, or stay in the car.
Once you approach someone, they have every right to defend themselves. And if they kick your ***, that doesn't give you the right to kill them.
I understand the point you are making here. Zimmerman thought the kid was doing something wrong so he approached him. Well the kid is the one who should be claiming the "stand your ground" defense in a situation like that. The kid was the one being followed by some strange guy with no badge.
You can't claim "self defense" if you were the instigator, you were the one who had a car and could have left, your life was never in danger, and as it turns out the kid was not even doing anything wrong anyway.
Starting a fight, and then getting beat up is not a reason to kill someone.
Let me ask you a question. If the situation went down almost the exact same (Zimmerman following him, chasing him, etc) but the kid pulled out a gun and killed Zimmerman (who was unarmed), would that be justified to you? I personally don't think there would be any question about it. And if that's the case, it's pretty hard to say Zimmerman was just defending himself simply because he was the one that had the gun.
You can't be the aggressor and claim self defense. Zimmerman was the predator here, not the prey.