I've found that most of the time even if you confront them with many of the inconsitencies of their possition they just tap dance around it
. I still present the entire argument anyway because, as has been mentioned, it might sew some seeds of doubt in the mind of the "apprentice" though the mentor is usually uneffected and will have a "counter argument" that tap dances around my argument instead of addressing it. I usually point this out as well (that the "counter argument" is not addressing my argument but "tap dancing" around it).