Has anyone ever seen someone that WANTS to believe in something so bad, whether it's religious or scientific or anything, and they know they are wrong but they just NEED to believe it and anytime anyone questions what they believe they react violently? That's the same with JW's. The GB reacts that way because it will uncover their lies. The Elders react that way because they are the whores of the GB and they are protecting their power. The average JW reacts that way as a behavioral instinct. I think alot of them KNOW that there are lies and deciets but their subconscious won't let that through to their conscious. So the subconscious tries to protect the consciousness by reacting violently to protect itself from the damage of knowing the truth.
The brain is an amazing and conflicted thing. Their are parts of your brain that operate in direct contrast to the rest of the brain. Like one part has it's own independent agenda. The subconscious is a very powerful thing and it will sometimes act against your best interests in an attempt to protect you from psycological harm. I think this is why the average JW reacts like they do when you contradict them.