The September 10, 2012 Washington Post points out the more likely explanation:
1952: The Congressional committee concludes there is no question that the Soviets bear blame for the massacre. It faults Roosevelt’s administration for suppressing public knowledge of the truth. The report also says it suspects pro-Soviet sympathizers within government agencies buried knowledge about Katyn. It expresses anger at the disappearance of the first Van Vliet report and says: “This committee believes that had the Van Vliet report been made immediately available to the Dept. of State and to the American public, the course of our governmental policy toward Soviet Russia might have been more realistic with more fortunate post-war results.”Unfortunately, wild enthusiasm for the murderous thugs of the Soviet Union was and remains strong among intellectuals in the U.S. and throughout the West. After all, their hearts were in the right place: socialism.