Ah yes.
There is a fine line between investing your intellect and perspective in participating in a conversation or taking your chips off the table due to the futility of your point to a person bound to a preconception.
At that point, I reserve myself to just listen and study to learn something about the topic or the person (if they mean anything to me.)
If I am prompted for a response, I just say, "That's amazing." Later on, when getting to know someone, I let slip that, when someone is making absolutely no sense, is just making excuses, or telling themselves a lie, I just respond with "That's amazing."
I think they will be open later, but I identified the tone very early and excused myself.
I think this is a good approach - I can happily sit and listen as it gives me food for thought anyway.
This made me laugh. A friend of mine says "That's special" when someone asks her about clothes she doesn't like. =)
oops - that was a pretty big comment vote - spend it wisely :D