Funny enough, I recall performing at Hershey, PA in 1992. We were just getting to our first big hit of the show (the big arc), and this one dude, sitting in the stands right in the center section, stands up and raises TWO middle fingers to the entire corps and just continues to stand there until the cut off! I believe he was "complimenting" the corps by basically saying "that kind of sound should not be allowed, F U and your glorious sound!!!"
Other members including Mr. Pink Elephant have correlating reports of seeing this that night as well.
It definitely made up for some of the riff raff we had to deal with that summer.