SOMEWHERE along the line the idea took hold that, to be an intellectual, you had to be against it, whatever “it” was. The intellectual is a negator and a dissenter. It wasn’t always so. In the World War II era, American intellectuals signed on for the war effort, and our foreign policy enjoyed bipartisan support. Liberal, conservative, moderate, even radical intellectuals found common ground in the struggle against fascism, without fear of betraying the lofty stance of dissent.  Unfortunately, the same cannot be said of the fight against Stalinism. Many on the left were reluctant to face the truth about the Soviet Union, with its mass slaughters and gulags.  This form of left-wing denial has resurfaced in the wake of the terror attacks of September 11.