At some point, differing opinions are going to be expressed. How you as the teacher react to those disagreements is extremely important. First, stay relaxed! You are going to manage the situation well, and it is going to turn out OK! Express satisfaction that people feel free to express their opinions, even if theirs are different from someone else's. You might say something like, “OK, we have differing opinions here, and that is great. Maybe there is even a third opinion that you would like to share.” Statements like that can relax the group, and often will lead to avoiding a debate over the two opinions presented. If that doesn't work, ask your class to discuss first the positives of each of the differing viewpoints, and then the negatives. If the matter is a serious doctrinal issue, you might thank the person for sharing his viewpoint, and then say something like, “Historically our church has taken a different view on this subject,” and then share what that position is. Avoid communicating a flat, “You are wrong.” Keep the conversation open. You may be surprised at the changes that can take place if you do!