It is error only, and not truth, that shrinks from inquiry.

Something solid can be poked at all day and stays where it is. What flinches from questions is usually what cannot survive them, which makes defensiveness a useful signal rather than an insult. Anyone who wants a claim protected from examination is telling you something about the claim.

Run the test in both directions. When a subject makes you want to shut down the conversation, treat that as an invitation to look closer rather than proof you were right. And be wary of any group, cause or person that treats your questions as disloyalty.