The 41-year-old mixed martial arts fighter Xu Xiaodong has been a controversial figure in China ever since he became famous for beating up what he called “fake” kung fu masters. Unafraid to talk about almost anything, his brash attitude has brought him stardom but also unexpected – and unwelcome – knocks on his door. In November, he set out to prove that he’s more than a tough guy who dared to challenge a cherished Chinese tradition. In the video above, Inkstone follows Xu, nicknamed “Mad…