What are the real reasons the jury is angry with Stargirl?

In Stargirl, Leo and his friend Kevin have a school television show called "Hot Seat." When they book "Stargirl" (Susan) as a guest, she is enjoying newfound popularity as a cheerleader. By the time of the scheduled interview, however, many students have returned to their original negative assessment of her actions. In a small town school where sports have an enormous amount of importance, the most visible symbol of aberrant behavior is her cheering for both teams rather than just for the home team.
The television show includes a jury interview format where multiple participants ask numerous questions. Although some of the strongest critics challenge her on the sports-team disloyalty, it is clear that the larger issue is their perception that she is mocking them. Unable to believe that Stargirl can be as detached from what they understand as their normal reality, her behavior has shaken them to the core. Her subversive behavior is encouraging them to question their own—and by extension larger social—values, and they are unwilling (or unable) to be that introspective. If they are wrong, they might have to change, rather than make her bend to follow their lead.