What do you want to achieve with your question? Are you genuinely curious about getting the details of the claim or do you have 100% confidence that the person is wrong anyway? Do you expect to gain something from discussing the topic further? It's completely okay that two people have different viewpoints.

You don't need to pretend that you accept it or to disagree to be able to move on. Whenever a topic doesn't seem productive and worth investing further energy you can move on.