Personally, in this situation I would try to redirect the conversation or talk about his father. I would ask positive questions such as "What is your favourite thing to do with your Dad?" This could help change his thought process to wanted to see his father to just having a simple conversation about him.

I agree with Ashley. When we visited a memory care facility recently, they were explaining how they deal with someone who is argumentative. Basically, its distracting them with something tbey know is enjoyable,to the patient. Discuss the behavior with his dr .... perhaps a chg in meds is in order.... Bless you ....