Well he is a nieghbor so I guess it would depend on if he PO'd me in the past and I hated his guts or I liked him ( or members of the family ).
If he was in the first catagory I would add a sign to his collection in the front yard, saying something like: the pot of gold at the end of the rainbow is here in an unarmed house.
If he fell into the second catagory, I would provide help, and shelter. I won't being arming a idiot though, he is qualified to keep the magazines full and make sure I don't run out of ammo. Anything more is a waste of ammo in my view.
The odds are he would fall in the 2nd category, I get along with all my nieghbors, oh well there goes my sign making project.
Fortunately I live in a very rural setting and the odds of it happening in my nieghborhood take the already very remote possibilty even slimer. Course two of my nieghbors are Highway Patrol and I don't think either of them is going to need any help, that only leaves two nieghbors in a country mile, and I know the Marine Corps gunny sergent can handle his own. Come to think of it our nieghborhood is not a good place to have anarchy in our counrty roads, and my guess is I couldn't find a anti gun nut for a least a mile or two, and my guess 90% of my nieghbors are already prepared.
I guess you folks in the cities and suburbs have different problems, but in the event it ever happens I would suggest armed nieghborhood watch forces. You would be much stronger with numbers and organisation on your side.