You might not consider the "kid" a "potential victim", although he was (because it's quite clear he became a "victim"). If he'd had a firearm, as you suggest, would that have prevented his assailant from firing on him?
In a few days we will hear more about this case.
Like any other tool, it can be abused or used for evil purposes in the wrong hands. People have been killed with hammers, wrenches, ice picks, even a leg of mutton (and that before it was cooked).
Anyone who claims to be a supporter of the 2nd Amendment should not need this spelled out for them.
In North Dakota, where I live, anyone engaged in criminal activity loses their ability to claim victimhood if they suffer injury in the process, by State Law. I am not familliar with Florida law.
We do not know (nor will we from the article posted) whether this was a lone incident, or just one more in a string of harassment. We do not know if the homeowner had other reasons to fear for his life, death threats, etc. which were unrelated to the kid. As far as victimhood goes, the fact remains that if the kid had not been screwing around on the guy's doorstep, he would have not been shot. That appears to be the first in a series of bad decisions which led to his death. Actions have consequences.
Now, before you twist that, I am not defending either party in this case. It appears, especially in view of your second post, that both were wrong, just one has paid more heavily for it at this point. What consequences they will have for the homeowner remain in the hands of the courts, but at the least, he can expect to lose everything he has unless he can mount an impressive defense.
Regardless of the actions of the persons involved, I still strongly believe that being armed is the first and best defense against the violent criminal element, and I will continue to embrace that responsibility.