The Communist regime considered dissent in the Soviet Union a repudiation of the proletarian struggle and a violation of Marxism-Leninism, and thus a threat to its authority. The proletariat was seen as selflessly striving for progress in the building of socialism, whereas the bourgeoisie was seen as selfishly fighting to maintain the status quo. According to Marxist ideology, class struggle was the engine of change in all social development. Vladimir Lenin's ideological contribution was to make the party itself the exclusive "vanguard of the proletariat" and thus the final arbiter of what was proletarian or bourgeois. The secret police was enlisted to enforce the party's ideology and to suppress dissent.
Because the party's legitimacy rested on the basic correctness of its ideology, failures in practical policy were never attributed to ideology itself. To maintain the party's ideological authority, religion had to be condemned outright, and history periodically revised to match the current party line. Books and magazines viewed as no longer politically correct were removed from libraries. Scientists, artists, poets, and others, including many who did not think of themselves as dissidents but whose work appeared critical of Soviet life, were systematically persecuted and even prosecuted. Often they were declared either enemies of the state and imprisoned, or insane and committed to punitive mental hospitals.
To speak for human rights or to support freedom of expression was to question the very basis of Marxism-Leninism and the legitimacy of the party's rule. Among those harassed and persecuted were world-renowned artists and scientists, including Nobel Prize winners Boris Pasternak, who was forced to refuse his prize; Aleksandr Solzhenitsyn, who was forcibly removed from the USSR; and Andrei Sakharov, who was expelled from the Academy of Sciences and internally exiled to a closed city.
A prime mover of change was Mikhail Gorbachev, whose policy of glasnost' allowed freedom of expression and resulted in the abandonment of Marxist-Leninist ideology and a loss of legitimacy for the party.
Mikhail Suslov autobiography