I think people going into it with a attitude that there is no God or that Jesus is this or that or that Christianity is this or that are going to get the same kind of walls as if they were trying to break down the Watchtower organization itself because faith and Christianity is still their Foundation so I think that someone coming up there with "all believers are idiots" attitude is not going to get very far with a Jehovah's Witness and any kind of conversation I think somebody questioning things, even things about faith or things about Jesus respectfully, even if you don't feel respect for them is important because otherwise they they will at least mentally plug their ears up and start saying blah blah blah blah blah blah blah because they can't hear you so I agree with the original poster here. That's not even a Cult response that is a human response because nobody can have a rational conversation when they are under attack like that even in the movies. They might be able to come back with a different attack but there's no communication going on.
So I would hope that if you want to have a conversation that you keep it in a tone that can remain conversational, rather than confrontational.