I would ask them if they read any of the literature in the late 60's and early 70's that indicated that 1975 was a really important year, and that Armageddon my come in that year. You might mention that the same kind of prediction was made for 1925. Also, I would ask them if they are allowed to read literature that is critical of their religion. If they say no, I would tell them that this is a double standard, since they encourage the householder to do that very thing, when they ask them to read WT literature.