if i claim i wrote a well-known novel, no1 can say i am fake unless the real writer stands up.
yeah you can say i have no education or training in writing, but that won't stand up in court as i can claim i am an unorthodox genius.
you can say i have no other publications, but quite some writers only have 1 famous product.
you can say i am shy or looks awkward, stupid on interivews (like han), but again i can claim i am unique that i can only write or speak in private, say, with close friends.
on the other hand han can never really prove he wrote all those things, how could he? it's all behind close doors. manuscripts with lots of modification marks? quite good, but not definite evidence, it can still be manipulated to achieve that effect. very familiar with all the writings? a big fan can also do that.
this is so unlike fang's previous fights. those he could easily win in a court of law because he held solid evidence. but not this time, all his logic and reasoning are good, but not good enough to become evidence in court. then han should never win either, as fang certainly is within free speech boundary, let alone with very persuasive arguments