Another one you may want to try when they have a really strong opinion or belief that doesn't make sense is to ask them why it is important to them. Not in a judgmental way but in a kinda curious tone (even if you don't care and are not listening). It sounds like what ever is going on is bringing up something for this person other than what they are going off about... some kind of old memory. Often we don't even know we are displacing our feelings. Asking what is important about _____ helps us stop and think.