I remember a Les Claypool mp3 like that, someone kept spitting on him so after a brief tirade he asked "would someone find the piece of shit that spit on me and kindly sodomize him? Thank you." Funny stuff.
I booed one band, one time. In a bar, while I was belligerently drunk, after they played a horrendous Tool cover (I love Tool, it was an extremely shitty cover). Even that was stupid, because I don't like heckling a band on stage. If you don't like them, go to the bar and wait for who you came to see.