Hi MissT,
I remember reading in a parenting book (!), "when you start arguing [with your 2-year-old], you've lost." Here's what I do when I'm with a previous identified N:
1. The intruder alert signal goes off...beep, beep, beep. Then when the lips start moving: OOGAH! Incoming!!

Take cover. Raise your invisible BS shield.
2. Do NOT take the bait. I repeat. Do NOT take the bait.
One cannot reason with irrationality.
3. I respond with a neutral "I'm sorry you feel that way," or "Thank you for sharing that with me," "Good luck with that," or "Hmmm, fascinating."
4. Change the subject. If this doesn't work, repeat step #3

as many times as you need to. Then go to the bathroom.
5. When all else fails, set lasers to stun.
6. Clear.
Over and out, S.