Jayne, I don't think the tears of humiliation came from the can incident, but from what followed, i.e. the man sitting in the the aisle across from her, yelling at her.
You just have to play this scene through in your own head, putting yourself in place of the woman, to see how unacceptable it was.
JJ: Can I have a can of diet coke?
Stewardess: There you go, madam [hands JJ a can of opened diet coke]
JJ: Oh sorry, can I have an unopened one please?
Stewardess: I'm sorry, I can't give you an unopened can.
[stewardess moves on]
Nearby chap: Can I have a beer please?
Stewardess: Sure, there you go sir.
JJ: Hey, just a minute, that beer is in an unopened can. Why can't I have a diet coke in an unopened can?
Stewardess: It's so you don't use it as a weapon.
JJ: What The Funicular?
Other nearby man: You need to shut the f*** up.
JJ: What?
Other nearby man: [leans over from seat, looks JJ straight in the eyes]: Yes, you know you would use it as a weapon so shut the f*** up.
[Embarrassed silence all around]
Bear in mind with all of the above: “There is no policy difference in serving alcoholic or non-alcoholic canned beverages to passengers,” says Bob Birge, director of corporate communications at Republic Airways Holdings, which owns Shuttle America, “no differentiation in opened or unopened cans, and no policy speculating what may or may not be done with a container.”
Darn right that stewardess needed some re-training. She made a complete and inexplicable hash of creating the situation and then not dealing with it very well. Here is how it should have gone, and almost certainly would have gone, if it was you JJ:
JJ: Can I have a can of diet coke?
Stewardess: There you go, madam [hands JJ a can of opened diet coke]
JJ: Oh sorry, can I have an unopened one please?
Stewardess: I'm sorry. Of course. There you go.
[stewardess takes opened can, gives JJ an unopened can and moves on]
Nearby chap: Can I have a beer please?
Stewardess: Sure, there you go sir.
[JJ notes to herself that he got his beer unopened]
[Nearby man rages quietly to himself, "Look at that jogger over there. I *** hate joggers]
[Congenial atmosphere all around]