Well, that's what I'm not going to get into. And I understand and I respect that argument. But I think I've got to line-draw here someplace. And I understood that argument before. And what I don't want to do here is turn this into an oral argument on things that I've already decided. And I know you respect that.
A decision has been made and they don't want to change their mind. 
The statement is definitely correct because in the context the person is adamant that they have decided and they don't want to argue further with people who want to change their mind. I suspect the system misunderstood the determiner 'their mind' to mean the mind of other person, not the person speaking. 