This scene is intense as fuck. They’re not pulling punches, and at the end, Buster’s cheek is swollen and bruised, and he licks his visibly split lip. Martin Scorsese cites it as inspiration for scenes in Raging Bull.
Buster didn’t jingle half the way.
Buster was a stickler for authenticity.
Oh, and I like to imagine that he’s punching Louis B. Mayer here.