What is interesting to me on this question is that the United States did not officially adopt a national anthem until 1931. Congress voted on it and "The Star Spangled Banner" beat out "America the Beautiful" by a single vote, much to the dismay of the Colorado delegation which had strongly pushed the latter. "America the Beautiful" was composed by a young woman on the summit of Colorado's Pike's Peak and its first stanza describes the view she enjoyed there.
So it has been only eighty years that the country has even had an anthem. Many people, not just Jehovah's Witnesses, don't like the custom of presenting the colors and playing the anthem at athletic events which have nothing to do with politics. I don't know how or why that custom arose. For my part, I stand quietly when the colors are presented and the anthem is sung. I will not, under any circumstances, sing any national anthem. My own personal belief is that nationalism and Christianity do not mix. That doesn't mean I don't appreciate being an American citizen. My father served honorably in the Army for twenty years, seeing duty in both Korea and Vietnam. My travels abroad have helped me to further appreciate what American citizenship means.
The fellow who talked on his cellphone while the anthem was played showed gross disrespect to not only the country but his countrymen. I don't blame them for being upset, and all the moreso since this disrespect took place in New York on the tenth anniversary of the terrorist attacks of 11 September 2001. He might as well flashed the finger while the colors were being presented, and I'm sure that is how his conduct was viewed.
As far as Jehovah's Witnesses and flags are concerned, they are inconsistent. You can't stand for the playing of an anthem, but should rise when a judge enters a courtroom and takes his seat on the bench. You can't salute the flag, but can sign a document swearing to defend the country's constitution if you want to secure a passport. Office holders are agents of Satan, but should be addressed by their proper titles upon meeting them. I don't pledge allegiance to national flags either and I agree that compulsory flag salutes are unconstitutional, but that doesn't mean that respect should not be paid to a nation's emblems, officers, and institutions. That's something the WTS can't seem to grasp.