I came across a 5 minute audio clip from Greg Koukl at Stand to Reason that was particularly fascinating and instructive. Most of us have had conversations with people who raise questions against a view we hold (like Christianity) but then keep “moving the goal line” as to what counts as a satisfying answer.
In this case, Greg is interacting with a lady who calls into the radio show. Give it a listen, and watch how he guides the conversation and most importantly does not get defensive (when he probably felt tempted to).
To learn more about how to navigate spiritual conversations, see Greg’s book, Tactics.