Yes, let’s reward that behavior with a treat in front of other people.
This is a situation that’s a one-off where someone not used to the normal customer experience reacted unreasonably. If you give in and allow their behavior to override the rules of doing business with that establishment, you not only encourage that person to continue acting out to get their way, but you also send a problematic message to the customers watching this interaction.
No. Working in retail is a direct exchange of goods for money. You follow the policies of that establishment, or you take your business elsewhere. You don’t have an actual tantrum over something so trivial and get catered to.
I’m now in a position where I have autonomy over what I offer to customers, and I agree with your principle. It doesn’t apply in this situation, though.