Dave Grohl in Tenacious D's The Pick of Destiny.

If you were planning on getting rowdy in the pit when the Foo Fighters roll into the Forum this fall for two nights of back-to-back rock-your-face-off n' roll, you better think twice. Dave Grohl might become enraged, publicly humiliate you while dropping about a dozen F-bombs and then toss you out of the concert.

Last night during the Foo Fighters iTunes Festival show at the Roundhouse in London last night, Grohl got very, very angry at a fan. Watch this:

"You don't fucking fight at my show, asshole!!" Grohl yelled. "Get the fuck out of my show right now, get the fuck out! ... You don't come to my show and fight. You come to my show and fucking dance, you asshole! ... I don't put up with that bullshit. You people come here to have a good time and that guy can fuck off."