Yes, they mention the Santa Claus thing. Click on the slideshow though - the city of Denver, for example, absolutely puts us to shame. Best quote from the article:
"If there is even a slight thought in the fans' minds that they should boo, they will, because it's a routine. It's expected of them," says Scooter Lammey, a Phils fan and independent filmmaker. "If someone discovered the cure for cancer, was announcing the 'antidote' to the world at an Eagles game and came out wearing a Cowboys jersey, he would be booed so loudly the world would never know the cure."