“As a group, please tell me three facts about <the topic.>. Raise your hand if you have a fact to tell me”
If someone says something that you suspect isn’t true, still write it up and don’t immediately tell them that they are wrong. Ask whether anyone else in the group is of a different opinion. If no-one else says anything, explain in a kind way why you don’t think that’s true. On the shared visible list, mark the disagreement next to this item, (perhaps add an asterisk and a note). Then move on.
People like to show that they already know something about a topic. It helps you get an idea of their prior knowledge.