As if there weren't enough reasons to hate the Damn Yankees:
At the Stadium, Stay Put When the Music Plays
The most patriotic moments at Yankee Stadium can also be the most confining.
Seconds before "The Star-Spangled Banner" and "God Bless America" are played, police officers, security guards and ushers turn their backs to the American flag in center field, stare at fans moving through the stands and ask them to stop. Across the stadium’s lower section, ushers stand every 20 feet to block the main aisle with chains.
...
Howard J. Rubenstein, the spokesman for the Yankees’ principal owner, George Steinbrenner, said the policy was an expression of patriotism.
Right ... an expression of the same patriotism that brought you Guantanamo.
More on the flip
"Yankee management is free to promote its brand of musical patriotism," Arthur Eisenberg, the legal director of the New York Civil Liberties Union, said in a written statement. "But we need to be wary of enforced cultural conformity and the use of a ballgame to impose political correctness on a captive audience."
Yankees officials said they adopted the policy in fall 2001 because of complaints that fans were not behaving respectfully during the playing of the "Star Spangled Banner" and "God Bless America." It's not entirely surprising, of course, that fans might be heading for the aisles during the seventh-inning stretch, with the cut-off of alcohol sales only a half inning away.
And meanwhile, over in Queens:
The Mets, meanwhile, have not heard complaints from fans about behavior during the songs and have not implemented similar restrictions, a team spokesman said.
I'll leave you to draw your own conclusions about the differences between Mets and Yankees fans.