I do not think it possibe to "reason" with any indoctrinated cult member, not in the true sense of the word "reason" any way. You can plant seeds of truth while they are not looking, but full on reasoning with logic and honest and broad assessment of a subject that threatens their world view? No, they will mentally cut you off everytime, and, if they feel you have gone too far (easy to do with a dub) they will politely pretend to "look that up" and just avoid you like the spiritual plague in the future.
Truth seeding is the best way to go, if you have the time and the patience for it that is.