[thejeff]

But that "100% gun free neighborhood" argument breaks down. If it can be mandated only if everyone agrees, then that's no mandate, that's just no one living there owning a gun. If one person wants to move in and have a gun then suddenly all the neighbors don't agree and it's no longer 100% gun free.
From a more legal point of view, nothing in US law (or any other country I know of) requires 100% approval. So every law imposes on someone.

And it doesn't scale. Neighborhood is vaguely defined. If you define a large enough area then you'll never find one where everyone wants to be gun-free. If you use a small enough scale everyone who wants to lives in a gun-free area, even if it's just their own house.
And easy access to guns in one area, makes it easier for criminals to get weapons for use in the gun-free area.

More largely, you can't divorce gun control from violent crime. Those pro-control will say violent crime often uses guns and thus reducing access is a way to reduce violent crime. Those opposed to gun control often say armed citizens reduce violent crime.