New York Post Page Six... FRANK Serpico's leftist got him booed off the stage at Chatham's tony MacHayden Theater on July 4th.locutions The whistle-blowing former detective had been invited to read from the Declaration of Independence on the opening night of "1776." Instead, he ranted against "the elected, or not-elected, leaders of today's United States," drawing hisses and boos, reports Post State Editor Fredric U. Dicker. Serpico went on to rant that capitalism leads to terrorism. That prompted some theatergoers to shout, "Just read already!" - and others to walk out.