The anti-Catholic Eurasians in the 1920s.
Archpriest Georges Florovsky (1893-1979) was an Orthodox priest from (Imperial) Russia, who was associated with what theologian Paul Gavrilyuk calls the Eurasian movement.
See Gavrilyuk's essay "Florovsky's Neopatristic Synthesis and the Future Ways of Orthodox Theology", collected in Orthodox Constructions of the West:
Upon his arrival to Europe, Florovsky joined the Eurasians, who to some extent followed the Slavophile trajectory [...] Florovsky contributed to...the next two volumes published by the Eurasians, On the Ways and Russia and Latinity .
The introductory article of [Russia and Latinity] advanced a claim that for the Orthodox believer in France to be converted to Roman Catholicism was worse than to be killed by the Bolsheviks in Communist Russia, on the grounds that the former led to the eternal perdition of the soul, whereas the latter caused merely a temporal destruction of the body. When this astonishing idea was criticized by Prince G. N. Trubetskoy on the pages of Put', the Eurasians promptly responded with an open letter in defense of their moral comparison of the repressive character of Bolshevism and Catholicism. Florovsky, who was one of the contributors to the Eurasian volume Russia and Latinity, had signed the open letter in question.
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When Russia and Latinity was published in 1923, the worst of the anti-religious fervor in the Soviet Union was not yet in effect. The anti-religious campaign of 1928-1941 was particularly anti-Orthodox, and killed as many as 200,000 Orthodox monastics and clergy alone, not to mention the numerous horrors inflicted upon and murders of the laypeople.
The Eurasians' view was apparently considered astonishing even at the time, and was clearly written before the full force of Soviet crimes against Orthodox people had been realized. The Fourth Crusade was certainly disastrous for the Orthodox Church, but I am skeptical of Ferguson's claim that most 20th century Christians would prefer Marxism (as the Soviet Union saw it) to crusaders.
For comparison from a less fringe perspective, Metropolitan Kallistos Ware (1934-) is a very popular Eastern Orthodox theologian, and for decades lectured about Orthodoxy at Oxford. In his The Orthodox Church (1993 ed.), he wrote:
In this way, from 1917 onwards, Orthodox and other Christians found themselves in a situation for which there was no exact precedent in earlier Christian history. The Roman Empire, although persecuting Christians from time to time, was in no sense an atheist state, committed to the suppression of religion as such. The Ottoman Turks, while non-Christians, were still worshippers of the one God and, as we have seen, allowed the Church a large measure of toleration. But Soviet Communism was committed by its fundamental principles to an aggressive and militant atheism. It could not rest satisfied merely with a neutral separation between Church and State, but sought by every means, direct and indirect, to overthrow all organized Church life and to eliminate all religious belief.
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