I echo the sentiment about calling Jehovah's Witnesses a cult. A person has to come to that realization on their own or they will become defensive. Instead I would reference the Three Pillars of Religion/Spiritual Practice.
- Dedication to finding the truth
Faith - You must believe in the teachings or doctrine. Belief is not knowing. It is a highly held opinion. "I believe these teachings will lead to salvation or, more importantly, to the end of suffering."
Doubt - This is not skepticism or the endless asking of questions. This is simply accepting that what you believe has not been proven. It is being open minded that you may find evidence that could either prove or disprove your belief. It is not accepting something as truth simply because a book or a religious leader says it is true.
Dedication to finding the truth - Truth requires examination of belief and proof through experience. Truth is eternal and must be experienced. Truth is not an intellectual process, but rather an experiential phenomena.
So, ask -
"Do you have faith in the teaching of Jehovah's Witnesses? Do these teachings bring salvation? Have the teaching brought to an end of any sort of dissatisfaction, fear, anxiety, regret, and sorrow in your life?"
The answer to this may be "yes" and may be "no".
"Do you have any doubts in these teachings? Are you allowed to openly doubt these teachings?"
We know the answer to this question, especially the second question, is probably "no".
"Have you diligently examined these teachings? Have you personally experienced the truth of these teaching? Do you accept these teachings because you proved them to be true or do you simply accept them because of something you read or were told?"
We know that in recent years the Watchtower has expressly forbid Jehovah's Witnesses to do their own research and have been told the Watchtower that they will tell Witnesses what to believe.
This line of questions shows that, at most, the religion of Jehovah's Witnesses only has one of the three pillars. In regards to question #3 you could also ask, "Is it not hypocritical that you are told 'Make the Truth your own,' but are also told, 'Do no research and accept only what we say'?"