"The Negroes in the United States constitute the most politically advanced group in the country. It is an oppressed and mistreated group. As a matter of fact, not a single inhabitant of Harlem believes the imperialist propaganda. Moreover, they have great importance in the world and any repression against the U. S. Negroes will be condemned by the Afro-Asian countries. We are thinking of presenting a motion in the United Nations against the racial segregation in the United States."

What does Castro mean by "imperialist propaganda"?