The general rule will be to back off a bit as already stated... however if you do occaisonally want to inject someone with the potential to think then as opportunity presents itself you may want to show them the Deborah Layton quote about Jonestown:
"When your own thoughts are forbidden, when your questions are not allowed and our doubts are punished, when contacts with friendships outside of the organization are censored, we are being abused for the ends never justify the means. When our heart aches knowing we have made friendships and secret attachments that will be forever forbidden if we leave, we are in danger. When we consider staying in a group because we cannot bear the loss, disappointment and sorrow our leaving will cause for ourselves and those we have come to love, we are in a cult... If there is any lesson to be learned it is that an ideal can never be brought about by fear, abuse, and the threat of retribution. When family and friends are used as a weapon in order to force us to stay in an organization, something has gone terribly wrong." - Deborah Layton
http://religiouscultsinfo.com/2010/07/%E2%80%9Cseductive-poison%E2%80%9D-by-deborah-layton-voice-of-a-survivor/
Another good line (not sure who's) is this:
"It's much better to have questions you can't answer, than answers you can't question."
I wish you well, but do get a firm grip on your tongue if you want a smooth exit.