LARRY Flynt and Robert Mapplethorpe may represent merely the most recent stop along the path our culture has traveled for well over a century. Though it is difficult to imagine, there may be worse yet to come. But then only a few years back it was impossible to imagine the public display of Hustler or Mapplethorpe’s photographs of homosexual sadomasochism.  The history of our decline, and the reasons for it, is elegantly traced and analyzed by Rochelle Gurstein, a disciple of the late Christopher Lasch, in The Repeal of Reticence.†