Oh look, there's video! Always seems to be, huh? The Sun, chronicler of the ages, tells us that Casey Affleck, Joaquin's brother-in-law and potential partner in hoaxery, was also in the crowd, filming away for this alleged documentary. The whole thing looks pretty staged—from Phoenix bragging about his millions of dollars in the bank, to the completely unsurprised and calm look on his face as he sets his mic down on the stage and heads into the audience for a bout of fisticuffs.
The audience was eating it up, chanting "Beat him up! Beat him up!", so that must have felt nice for Phoenix. No matter how out-to-lunch on various handfuls of drugs he may be, which Phoenix undoubtedly is, a performer still enjoys, nay requires!, the love of a sweaty, heaving audience. So even if it's a tiresome, indulgent meta joke, we're all at fault for perpetuating what has become an all too real and sad personal history.