Thanks You M'am is different from what readers expect because of the trust the characters display to the readers. In modern society, if something like that would happen then -
1. The woman would scream
2. The woman would call the police
3. The boy would not be taught a lesson
The theme of the story is forgiveness. People have a hard time forgiving one another. In the beginning of the story, you would expect Roger to be some kind of delinquent, while Mrs.Luella Bates Washington would be the victim of a robbery. As the story progresses, you learn that Roger is actually a poor boy wanting blue suede shoes, and Mrs. Luella Bates Washington a woman with a strong forgiving heart.