If you are dissatisfied with the free thing I gave you, then I am happy to send you a refund of your purchase price. π€·ββοΈ
That's my preferred strategy.
UPDATE: Before any angry cards and letters, let me clarify. When I reply this way, I learn a lot about the person I'm talking to, including whether they are prepared to have a reasonable conversation about this complex matter. The response I'm hoping for is "Well played.", because that tells me that they recognize how ridiculous we are both being. I can work with them.
If they are merely having a tough time and needed to vent, then they'll notice that and we can move forward.
If they are truly that entitled, then I don't mind what happens next, because they would probably never have accepted any help I could offer them, anyway.