This is wrong. FF makes no personal claims. He is what we call a "no claimer". If you ask him for proof of a claim he made he will point out that was not what his words meant. His command and use of the English language is not anything most people use. If he says something that bites him later he changes the meaning of the words to cover this up.
There is no possible way to meet his challenge because he is the only one that can decide what is credible.
Personally, unless you're in the mood to swat flies, ignore him like the rest of the world (with the exception of his "lurker" army

).