One way to deal with people who buy into the myth that people don’t need guns in a society with a modern police force is to offer them an 8.5″ by 11″ sign announcing “This house is GUN FREE”.
They look especially good when printed on Canary yellow paper and can be produced inexpensively on any printer.

Offer one to the next person who makes the old “you don’t need a gun, the police can protect you” argument and ask if he/she would be willing to post it in the front window at home.