Speaking from personal experience, often the person with dementia does not believe there is anything wrong. For famous / powerful / rich people, the family is actually at a disadvantage as the person has believed in their super power too long. They cannot reason. It’s not “won’t listen,” really. It’s CANNOT. Reason has left the building. And they can fool people. With extra effort they can appear normal for short times when they really try.
So let’s say he is within the scope of what you have dealt with.
If someone shows him the questioning today ..that CLEARLY shows he was confused...do you think he could be reasoned with it.
Or does the mind not even recognize that he said President Comey, etc.