The worst part is that this idiot will probably go around telling all of his friends that you were "so afraid of his bushido skills that you wouldn't fight." If vale tudo style fighting is so simple and so beneath his master-level-abilities, then what is stopping him from fighting you and cleaning your clock, proving once and for all that kowtowing and doing kata all day long really does make us into Kung Fu assassins? This is the same type of pseudo-black-belt that Bob Orlando talks about in his book Martial Arts America (a great book, by the way). Some guys know either consciously or subconsciously that they can't fight, at least not up to the level that all their self-hype would suggest. Thus, they repeatedly make excuses not to spar so that they can continue to run their mouths and yet not get hurt or be forced to actually prove their abilities. After trash-talking JKD so much, this guy has nothing to win by sparring: either hell freezes over and he wins the match — so what, he's a "Master" and it was expected of him — or he looses the match and looks like a total chump (especially to his students/followers). Unfortunately, this type of invertebrate will do anything to avoid a real conflict, so I doubt there is anything you could (legally) do to make him spar with you. Then again, you could always run over him with your car and then sue him for carelessly damaging your motor vehicle.
Take care and train hard,
Jim McRae