But then you cut straight to the root of all their assumptions and show how absurd that is, thinking they'll have the wherewithal to realize that it recursively debunks every belief or claim they've based upon it, but then they hit you with the "What does that have to do with this? Why are you changing the topic?"

That's when you know they can't be reasoned with...

I'm not 100% sure, but I think AronRa came up with it, or is at least the first person I've heard use it.