Humans will believe things that are false if it benefits them personally. It is a defense mechanism of the Ego, which in itself is a mental illusion. A sudden end of the Ego when it is not self induced is a traumatic experience and can cause post traumatic stress disorder. In short, the new information presented is in conflict with highly esteemed beliefs. The brain sees this as an attack on the belief holder (which it isn't) and acts accordingly - an emotional response. The easiest quickest response is anger or to attack.
I think some people might point to the Sunk Cost Fallacy, which is an economic concept that sometimes can be applied to areas of or personal lives. This is why it is so hard for born-in Witnesses who reach their 40s, 50s, etc. The more time in the harder it is to get out of the Sunk Cost Fallacy.
Description: Reasoning that further investment is warranted on the fact that the resources already invested will be lost otherwise, not taking into consideration the overall losses involved in the further investment.
I believe that reason number one is most likely the answer. Be presenting the father with evidence that his beliefs are inaccurate the mental construct of himself (Ego) is perceived to be under attack. The brain responds the same as if he were under a real attack of a physical danger such as a dangerous, wild animals or physical assault from a person. Logic, reason, and rational thought are unable to function when emoting.
If the person were to genuinely and compassionately ask their father what the father was feeling when pinned down with the question, it is my belief the father would respond with "I felt angry."
