It's considered impolite to interact with someone's service dog.
Marty sees a service dog with it's owner on the street.
Marty wants to acknowledge the cute dog.
Marty smiles at the dog and tells the owner it is cute.
Marty kneels down to the dog, petting it.
The owner thanks Marty for respecting that their dog is working.
Marty is sharply reprimanded by the owner of the dog.