How did Ivan Pavlov criticize the Soviet government after the Russian Revolution?

Ivan Pavlov was a bold nonconformist who openly criticized the Soviet government and communism throughout much of his career. His opposition included several notable actions:

• Refusal of Privileges: During the famine following the Russian Revolution, he rejected special food rations offered by Vladimir Lenin unless they were extended to all his collaborators.1
• Public Denunciation: After visiting the United States, he publicly declared that the basis for Marxism was false and famously stated he would not sacrifice a frog’s life for the Soviet social experiment.1
• Resignation in Protest: In 1924, he resigned his chair of physiology after the expulsion of priests' sons from the Military Medical Academy, identifying himself as a priest's son.1
• Direct Confrontation: He wrote to Joseph Stalin in 1927, expressing shame at being called Russian due to the government's treatment of the intelligentsia, and later refused to allow Soviet official Nikolay Bukharin entry into his laboratory.1

Late in life, Pavlov’s stance softened as government support for science increased.1