Dave Grohl is renowned for being the nicest guy in rock and roll, he's constantly happy, and he loves his job. Why shouldn't he?! He's a lover not a hater would be a fare assessment I think. Earlier in the week at the iTunes festival he proved this when he spotted fans fighting in the crowd mid song and promptly stopped the set. He called out the fan in question saying: "Stop! Stop! No. You don't fucking fight at my show you asshole! Who's that? Right there! Let me see him! Who's fighting right now? Who's fighting?...." This went on for a little while and Dave got the offender kicked out of the show, much to the joy of the fans. "You don't come to my show and fight, you come to my show and fucking dance you asshole!" he finished with. You can witness the moment at the top in the video.
So if you're gonna go watch Foo's anytime soon on what seems to be another never ending tour don't cause trouble or the nicest guy in rock may look upon you so kindly!