Perhaps it was only appropriate that an exclusive cocktail gathering to celebrate gadfly director Alex Gibney’s doc on Julian Assange, “We Steal Secrets: The Story of WikiLeaks,” was in a subterranean spot. The Beatrice Inn hosted the party for the film that has sparked feuds between Gibney and an army of Assange acolytes, including Oliver Stone, even before its May 24 release. (Gibney has said of a Stone Twitter diss about the doc’s being “unkind,” “[He] denounced the film and me . . . though he hasn’t seen the film. It’s kind of pathetic.”) At a Tribeca Grand screening were Graydon Carter, ex-Universal co-head Marc Shmuger, Clear Channel’s John Sykes, John Leguizamo and David Steinberg.