Both of them are inexcusable.
In life you’ll encounter assholes; this is a given. How you deal with them shows what kind of person you are.
Jack, on realizing he was dealing with an asshole, should have ordered the goddamned English muffin. What would it have hurt him to eat an English muffin? What kind of Little Lord Fauntleroy gets all persnickety about something like this? Bitch about it in the car afterwards and move on with your life.
The waitress, on realizing she was dealing with an asshole, should have at the very least have apologized for the inconvenience. She should have helped him figure out how to order his Very Special Meal. When Jack figured out how to order his Very Special Meal, she should have smiled at his cleverness and gotten it for him, instead of continuing to sneer at him. Bitch about it in the kitchen afterwards and move on with your life.
But both of them chose to be assholes, and consequently we got an entertaining scene.