DM: The NPC succeeds his his persuasion roll, so you hand over the McGuffin that is in your hand.
Me: I would never do that, so I refuse.
DM: Sorry, I've determined that it wasn't beyond the realm of possibility and the die roll succeeded.
Me: But I would never do that, so I refuse.
DM: You hand over the McGuffin anyway, since the persuasion check succeeded.
How is that not the equivalent to mind control and loss of my agency to decide what my character does?
It's not a False Dichotomy at all. Either I have full control to decide what my character thinks and does, or I don't. There is no middle ground where I still have full control(100% agency).