1. Remind that these discussions are not a contest of who is right or wrong.
2. Ask for people to keep in mind that this is about trying to learn about the differences in the religions not necessarily understanding the differences.
3. Advice people to be open to listening to the differences and they must resist the urge to jump in and state why they think the theories are right and wrong at the moment of listening to differences.
4. If possible try to divide the discussions into varies topics which are preset to allow for preparation and to help keep defenses down. When people feel prepared their is a chance of feeling more comfortable and not feeling that their religion is under attack. It is about listening, learning, and discovering different religions.
5. Make it clear these discussions are not about changing someone's religion and are not about constantly trying to persuade to change. It is about learning the theories, history, practices and about different religious cultures as a whole.
6. Advice and have people understand that when others ask questions it is not about attacking them and/or their religion it is about research.
7. If at any time anyone in the group does get verbally aggressive and starts to rebut or starts personal attacks or comments make it clear they will be banned from the discussion. For example, Blue says Blue walks always on the right lane. Red says Red walks always on the left lane. Yellow states "you are all stupid, everyone knows the right way is to always walk in the middle." This particular Yellow is should not be in the discussion, find another Yellow who is more mature and understands the purpose of the discussions. Blue and Red are stating how they practice their religion and so they each can learn. Yellow is also stating how they practice their religion but is confrontational and will delay the research and learning process for all and is instigating arguments.
8. I would also recommend to advice all that these discussions are also based on a small group's opinions, interpretations, observations, and does not mean that everyone in the same religion sees it exactly the same way. In another words just because on Yellow is being immature not all Yellow's are immature.
Hope this helps. Let me know if you would want more tips. I don't know if this is just a theoretical question or something in which you are really going to partake. But some of my best memories have been great discussions and learning about different religions. :) Good luck!