'Philadelphians would boo Santa Claus' - old saying.
Back in 1981 I was at the old Vet watching Eagles vs Steelers in a pre-season match. The national anthem was sung that day by Barbara Mason, who had had a few hit singles in the 1960's and early 1970's ('Yes I'm Ready', 'Give Me Your Love')...when she hit 'rockets' red glare' her voice cracked, and a cascade of boos came from the stands.
It was ever thus.