There is a new field of sociology that has been developing over the past decade. It's called "wrongology." It's the study of how people act when they are wrong.
According to "wrongologists," people like the Jehovah's Witnesses are not necessarily delusional. They are just acting the way all humans do with regards to their convictions. Part of it is a survival instinct, part of it is learned.
The instinct part involves the building blocks of experience that act as a foundation for logic. As infants and young children we learn lessons and store what we learn away to build more things upon them. In this process we don't second-guess our primary lessons. Once we learn that fire is "hot" and will "burn" us, and that getting burned "hurts," we don't have to touch fire a second time. We transfer the experience to reasoning that other "hot" things are equally "hurtful." We avoid touching radiators, hot plates, steaming water, etc., almost naturally after we learn the primary lessons. Without this instinct, not only could we not progress in learning, we would never learn to move forward.
But the learned part is what screws up people like the Jehovah's Witnesses. It can even make a stubborn ass out of Baptist, a Jew, even an agnostic and an atheist. Scientists and other critical thinkers can even get messed up because of this learned feature. What is it? It is that in society we are taught from childhood onward that being wrong is "bad."
Wrongologists have discovered that since we have given being wrong a moral label, "bad," the first instinct takes over and we avoid being wrong, believing we are wrong, and even accepting evidence that we are wrong when we are made to face it.
In reality, being mistaken or wrong has no moral value. Neither does being right. But, for instance, we reward when children bring home good grades from school and punish children when they bring home bad grades. This type of behavior in itself is part of the learned behavior that causes the problem. We don't take into consideration that a child may have cheated to get the good grades or that the bad grades are a sign that the child is still trying their best but merely incapable of doing the work assigned. We have developed a society where "gold stars" are given for success, and the whip for failure. This is why many successful people are in reality corrupt, and those who may have failed through school often very honest. Success is not a virtue, and failure is not a sin, but we have been taught this and teach this to others.
Since what we believe about ourselves and the world around us (as well as our place in it) gives us our identity, whenever these convictions are challenged by others we instinctively fight back. In most cases this is normal and necessary. If someone is trying to argue that you are a jellybean and that your life is actually the dream of a drunken frog, you can't accept that. Reality, to an extent, is based on what we believe, how we perceive it.
But if our beliefs are wrong, this instinct to protect our understanding can get in the way. Add to this that we have been taught that being wrong or mistaken is "bad," and the problem has just become like adding fuel to an already wildly burning fire.
Evidence and facts, even the best reasoning will not help. Because what you believe gives you your sense of identity, any attack on your convictions is an attack on you. And if your beliefs are like that of the Witness, where you believe your convictions come from God, being told you are "wrong" gets interpreted as being told you are evil, that your beliefs are evil. Who else but the Devil would claim that beliefs that come from God are evil? So how does the instinct of defense come back? It goes into denial. It ignores. Nothing, not even facts can get through at this point.
And Jehovah's Witnesses aren't being stubborn at this either. Scientists can hold on to theories they prefer even when the evidence is to the contrary. They have been known to bitter fight and resist new theories as they come. A person who is an agnostic or atheist can act the same way too. The Communist regimes are examples of atheists who don't want to believe they are mistaken, even when they slaughter by the millions those who bring the truth of their failings to light.
Finally (and it's even worse news), things like pride and stubbornness and anger can also come into play on top of everything else. This means that a person who is told they are wrong not only has their instincts and primary learning to overcome, their own pride and stubbornness and misbehavior can betray them even further.
So don't be too naive to think that the Witnesses are just being ignorant or stupid. They are acting just the way you do when someone tells you that you are incorrect.
Don't believe me or any of this? Then merely stop and think. If I said everything each poster on this thread wrote was wrong, wouldn't the normal response be to prove me wrong and each person to defend their view while trying to prove they are correct (even if each poster may have totally different views). Each different view cannot be right, and you, just like me, don't like to be told you might be wrong.
Add a cult into the picture that is controlling your every move, and it is just an even harder mess to untangle.