In To Kill a Mockingbird, what is Atticus's response when the children ask him to borrow a gun?

Shortly after the Tom Robinson trial, Bob Ewell confronted Atticus outside the post office, where he cursed him, spat in his face, threatened to fight him and promised to kill him. Atticus turned the other cheek and walked away, but Jem and Scout were worried about the death threat. Scout suggested that since Atticus was once the deadest shot in the county, he should get a gun for protection. Jem assured her that Atticus wouldn't carry one because "he told me havin' a gun around is an invitation to somebody to shoot you." But Jem decided to suggest that Atticus borrow one anyway. Atticus' response: "Nonsense."