First thing we have to do is what the Bereans did in Acts 17:11. We have to check out what that individual says against the Word of God. We should be doing that as a matter of course.
The Sunday message or the Sunday school lesson should not be our primary input in our walk with God. That should be a supplement. A conversation, albeit internal, between the pastor or teacher’s study and ours. If we find that their study has become our primary input. Some things should change in our priorities.
If we find something that does not seem to line up with our understanding of Scripture in the message, lesson, or book, the first question should be am I understanding the Bible correctly. It is possible that I may be in error. Second, I need to reexamine what the individual said I may have misconstrued or misunderstood what was shared.
If after that there still seems to be questionable content, if you have access to the individual, the next step is to discuss it with him. It may have been simply an unintentional misstatement, or your input will serve that individual in their pursuit of knowing God through His Word.
If you do not have access, resist the pull to discard all that was shared by the individual. Rather, discard the error and choose to embrace what they said was true.
The point here is that in all cases we need to be interactive listeners and readers. We cannot accept all that we hear or read uncritically. There is too much at stake.