I'm a big Who fan and one of my favorite "rarities" bits from their "Thirty Years of Maximum R&B" box set is the audio from the moment you mention. Hoffman is droning on in his arrogant, nasally voice about John Sinclair when you hear Pete loom up in the background "Get off me f---ing stage!!!" It never fails to bring a smile, I tell ya.
From what I've read supposedly Townsend hit Hoffman with his guitar. Hoffman committed suicide in the early nineties after his dream of a commie U.S. vanished. I've read some of his "literature", and it appeared to me that communism was just a tool for his own self-promotion. He was an obnoxious, egotistical, Marxist punk.