As war protesters marched toward Arlington Memorial Bridge en route to the Pentagon yesterday, they were flanked by long lines of military veterans and others who stood in solidarity with U.S. troops and the Bush administration's cause in Iraq. Many booed loudly as the protesters passed, turned their backs to them or yelled, "If you don't like America, get out!" Several thousand vets, some of whom came by bus from New Jersey, car caravans from California or flights from Seattle or Michigan, lined the route from the bridge and down 23rd Street, waving signs such as "War There Or War...