My Aunt is the same way about the show. I was babysitting my cousins and the show came on so we sat down to watch it... and I didn't realize that they were not allowed to watch the show. But they were all excited [it was the Bato of the WaterTribe Episode] and she came home to us watching that and she explained to me that she didn't want them watching that show.
She didn't give me a reason but I thought it curious because she's let them watch Caddyshack, Harry Potter, and shows like that I wasn't sure what she has against Avatar. But my cousins were super exicted because they got to see the show.