>In your example you would be saying you want apple pie because it gives you all these vitamins.

No. I just want it. That's the part you don't seem to get. It's a preference. There's no reason or rationale that you can attempt to short-circuit with any fact.

>ts the floating table. You knock all the legs of their argument down and

They're not arguing with you. They're attempting to tell you that this is their preference. That they won't change their mind. Sometimes they're bad at it, can't articulate it. Other times they say this perfectly clearly... doesn't much matter, because you're not listening. You hear what you want to hear (like above, with "you think the apple pie has vitamins!").

>and their belief only gets stronger. They are not switched on.

It's not belief. That's actually frustration. And a little bit of spite.