Bring back the Brooklyn Bridge flag! That was the cry yesterday from veterans alarmed by the apparent theft of a U.S. flag from high atop the bridge by anti-Bush protesters. The battle-tested veterans took aim at the suspected thieves and held out hope that the Stars and Stripes had not been destroyed. "It's disgraceful," Vietnam veteran Tom Shannon, 54, said from VFW Post 107 in Marine Park, Brooklyn. "They should be prosecuted. I believe that 100%." In order to hold someone accountable, cops first must determine what happened to the missing 12-by-18 foot banner. NYPD officials said they were investigating...