I would be loving and kind and welcome them to MY world. Let them see by my reaction that they were lied to all along.
@carpediem: I'm with you on that! I do fear a collapse of the central power structure would lead to new groups with similar tactics. I recall reading about splinter groups (Millenial Dawn, etc.) forming when JF Rutherford siezed control of the organization. Give the survivors something sane to cling to, an alternative to the next smooth-talker looking for new followers.