Raised by firefighters from the smoking wreckage of the World Trade Center, a flag telegraphed both anguish and resolve. Around the globe, flags — some of nations, others of affiliation — have wrapped spectators at soccer matches and participants in protest marches, flown over revolutions and holy wars, adorned advertisements and marked lunar landings. The man police charged with the attack, Dylann Roof, posted photos online showing him burning a U.S.