It's certainly true that adults and parents who are connected with a community are going to do their best to defend it against rogue individuals. Speaking as one parent - we would see it as protecting our children. This is one good reason why individuals who want to "bug out through a devastated city" need to keep a low profile, and avoid contact with citizens a lot of the time. But anyone who is peaceful and cooperative is likely to be welcomed, and integrated into the support structure.

However, if the "Rambo's" form themselves into coordinated groups then things might not be so simple. Maybe in the event that a major American city becomes a "mega-disaster", then things might turn grim. There would have to be a failure of all the survival mechanisms that hold communities together. Then it's conceivable that a more intense struggle for existence could ensue. It would be a situation like what happened in Stalingrad in Russia during WW2. The German soldiers called it "rattenkrieg" (rat-war), and it is depicted in the movie "Enemy at the Gates". I can only imagine this scenario happening if things become apocalyptic.

cheers,
Pete #2