What's wrong with the unknown unknowns defense?
"We can't know anything about an unknown unknown, so it serves no useful purpose. To use Bertrand Russell's famous illustration, we can't know for sure whether or not there is a teapot in orbit between Earth and Mars, so asserting that there is, is no argument in favor of such a teapot."
https://medium.com/@marktraphagen/yes-there-are-some-known-knowns-and-they-arent-going-to-change-d9307bee4750
Posted on FB by Duane Forrester