Unless you are going to train with him, who cares who he is or whether he is a liar.
I have to disagree.
Frauds such as Dux and "Ashida Kim" not only rip individuals off, they tend to write stuff about martial arts and it history that are totally false. And their stuff, because it is not bound by the need to be accurate, is more interesting and more widely known.
So the damage to the knowledge of not just ninjutsu history, but martial arts as a whole, has been severely damaged by people like Dux. We had a member of Dux's group here and he did his best to make Dux look good no matter how he destroyed the truth. If he had been allowed to go on without confrontation a lot more people would be facing stupid questions and false ideas about the martial arts. One person on one talk site can't do that much damage, but it all adds up.