I didn't notice that he was referring to one particular incident. The "stand your ground" law in place in many states is, I believe, what he was referencing. And, as I understand that law, you are entitled to shoot someone with impunity so long as they are advancing on you or your property.
This is a Canadian forum. You may find that many of us Canadians have a biased attitude to the US love of the gun. You might want to grow a thicker skin or at least keep that in mind so you don't come across as overly defensive.
From my experinece reading US based forums the same question posed by the OP would have had at least one poster within the first five or so saying "shoot the bastard".