In 1970's among Catholics of Latin America the movement arisen called "Liberation Theology" that essentially backed Marxist Regimes and movements in the region. John Paul II stood firmly against this movement, and I believe he excommunicated bishops who were supporters of the Marxist movement within Catholic Church. He knew very well what Communists are capable of and he was firm against infiltration of Communists and their ideology into the Catholic Church.
This group know very well that during Russian Civil War, Bolsheviks brutally murdered thousands of Orthodox Priests throughout former Russian Empire (incl. Ukraine). So those who claim to be Orthodox Christians and cavort with Communists, simply abominate the memory of those murdered, tortured and imprisoned Orthodox Christians.
They dance on the blood of real martyrs. It's sick.