“ The Board may determine an organization to be ‘communist’ if it is found that such organization engages in activities which seek by unlawful means the establishment of a government in the United States which is based upon the revolutionary principles of Marxism-Leninism, which interprets history as a relentless class war aimed at the destruction of the existing society and the establishment of the dictatorship of the proletariat, the government ownership of the means of production and distribution of property, and the establishment of a single authoritarian party. ”