Wikipedia: The Who performed at the Woodstock Festival that year , insisting on being paid before going on stage early on Sunday morning when they played much of Tommy. During their performance Yippie leader Abbie Hoffman sat on the stage with concert organiser Michael Lang. Hoffman had been working the medical tent since the festival’s opening act and was under the influence of LSD. Hoffman had become increasingly determined to publicise the case of John Sinclair, who had been given a 10-year jail sentence for passing two marijuana cigarettes to an undercover narcotics officer. Hoffman jumped up and grabbed a microphone during a brief lull in The Who’s performance of Tommy saying, “I think this is a pile of shit, while John Sinclair rots in prison!” Townshend replied, “Fuck off! Fuck off my fucking stage!” and struck Hoffman with his guitar. Hoffman leaped off the stage and disappeared into the crowd.
[Mr. Townshend had a few more choice words, oh my yes.]