Friend wants to pay off his mortgage with all loan, he's crazy right?

A fried told me over beers he is planning to pay off the last of his mortgage with an unsecured loan as he can borrow to cover what's left. His wife is fully against it, his daughter is fully against it, and I am fully against it.

I tried to explain that is a stupid idea as the interest rate is much higher and he is better off paying it off at his current rate but he seemed adamant. He has over a decade left.

I THINK he is off the mind that a certain large supermarket chain is going to buy the land he lives on as there has been inklings from various sources, and he believes he will be better off owning it full.

How do I convince him this a bad idea.