There are a few things I'll touch on. Firstly, free speech is a point of much contention among far left theorists. There are advocates for free speech in helping bring about the revolution, and there are other theorists who believe that it can be detrimental to socialist states as they transition to communism. Rosa Luxemburg, leader of the German Communist Party until her murder in 1919, was a proponent of the former. Luxemburg was largely critical of the Soviet Union's stance on free speech, saying that, "Freedom is always and exclusively freedom for the one who thinks differently."^1 This idea differs from that of Vladimir Lenin, who described free speech as, " a bourgeois prejudice." To him, free speech was a tool of the counterrevolutionary to subvert the socialist cause.

Subversion of leftist movements through free speech does have a strong historical basis to it. In 1951, social democrat Jacobo Arbenz was elected President of Guatemala. At the time, much of Guatemala's economy was dominated by the banana trade, of which United Fruit controlled most of. In order to jump start the Guatemalan economy and put people to work, Arbenz implemented a plan to nationalize the unused land owned by United Fruit. While not a completely revolutionary idea, United Fruit did not take kindly to the government taking their lands. United Fruit's board of directors at the time included CIA director Allen Dulles. Dulles and his brother, another board member, hired renowned propagandist Edward Bernays to launch a misinformation campaign to paint Arbenz as a communist. This included newspapers, radio broadcasts, and airplanes flying with messages, all of which was legal to do under Guatemalan law. As this campaign picked up popular support in the United States and within the Guatemalan military, the CIA aided a coup d'état to install a military dictatorship run by Carlos Castillo Armas.

During all of this, a young revolutionary by the name of Ernesto Guevara was living in Guatemala city at the time. Guevara believed that the freedom of the press within Guatemala was a contributing factor to why the United States were able to undermine the president. Guevara took his experiences with him first to mexico and then to Cuba. Determined not make the same mistake as Arbenz did, Guevara and Castro implemented controls over free speech to suppress counterrevolutionary, reactionary, and hate speech.

T;DR- Free speech is a point of contention within leftist theory, history has shown counterrevolutionary forces to use free speech in order to topple leftist governments, thus the explanation for the limits on speech.

sources:

• ^1 Rosa Luxemburg, "The Russian Revolution". https://www.marxists.org/archive/luxemburg/1918/russian-revolution/ch06.htm

• Colby, Jason M. The Business of Empire: United Fruit, Race, and U.S. Expansion in Central America. Ithaca: Cornell UP, 2011

• Klein, Naomi. The Shock Doctrine: The Rise of Disaster Capitalism. New York: Metropolitan /Henry Holt, 2007.

Edit: spelling, its late

In postwar Czechoslovakia, the Czech Communists won over a free press and created a national discourse in which even their political opponents had to concede that the Soviet Union represented Czechoslovakia's key ally. Propelled by their victory in this open discourse, the Communist Party became the largest of five parties in Prague's parliament after the elections of 1946, bringing Clement Gottwald to power as prime minister (Bradley Adams outlines the Communist victory over the national discourse in his The Struggle for the Soul of the Nation: Czech Culture and the Rise of Communism (2004)). After Gottwald seized power during the political crisis of February 1948, he totally bowed to Soviet pressure and seized control of the press. But for a time, a free press served his Party's interests; without the open debate that took place in the free press, Gottwald may never have been in a position to seize control on Czechoslovakia.

Later, the Slovak leader Alexander Dubcek freed the press in Bratislava (the Slovak capital, which had little power in Czechoslovakia as Prague dominated the union) as part of his generation of Communists struggle against the old guard that took power in 1948. Dubcek's generation of Communists had come of age during the Second World War, and though they also believed that the Czechoslovak alliance with Moscow represented a key component of Czechoslovak foreign policy, they also believed that certain liberal reforms (under the careful guidance of the Communist Party of Czechoslovakia) would bring "true socialism" to Czechoslovakia. Czech writers blacklisted in Prague flooded the Slovak press, Dubcek became a favorite among the younger generation of party officials, and he rose to power in 1968 over all of Czechoslovakia. He and his coalition then freed the press across Czechoslovakia, creating goodwill for Dubcek and his policies. True, the free press often criticized certain aspects of Dubcek's reform (or lack thereof) movement, but by freeing the press--along with other reforms--he became on of Czechoslovakia's most popular leaders in all of history. The Soviet Union did not like the anti-Soviet articles that appeared in the Czechoslovak press or Dubcek's apparent willingness to pursue a "Czechoslovak road to socialism" in clear contrast to the Soviet model, and the Soviet Union led a Warsaw-Pact invasion of Czechoslovakia to quell Dubcek's experiment (and, of course, used their post-invasion influence to end the free press). For Dubcek's take on the free press and its role in generating goodwill for the Communist Party and thus empowering the party to implement "true" Communist reform, see his memoirs, Hope Dies Last: The Autobiography of Alexander Dubcek (1993).

In short, opposition to a free press, while the norm among Communist (I capitalize the word here to indicate those states run by the Communist Party) states, it was hardly a universal truth.