It was the hysteria over communism, a peril that would consume the entire world, the political right ranted, unless we surrendered our constitutional freedoms to combat it. Just as we are now being told we must surrender our constitutional freedoms to combat "terrorism."
It is the oldest and probably the most-successful systems of government ever devised. It was a primeval system that served ancient societies well. It just didn't fit with an advanced economic world. The discord in the philosophy of Karl Marx is that one had to be highly intelligent to read and understand what he was saying, but one had to be a fool to think his visions would actually work in a modern world.
Ancient hunter-and-gatherer tribes used the collective to survive. The males would hunt in unison to track down and kill prey, to protect the village as warriors and to construct what was needed. The women would work in unison gathering herbs and berries, preparing communal meals and in raising children. For that society, collectivism worked well for hundreds of thousands of years. Marx and Friedrich Engels even praised American Indian tribes living in such enclaves for their internal peacefulness and absence of crime to argue for that social system to replace the misery-filled and crime-ridden capitalist society in which they lived.
The American political right praises the Iroquois Federation and its system of self-rule as the basis of the US Constitution. In "Origins of the Family, Private Property and the State" Engles did the same as a basis of scientific socialism; i.e. Marxism.
Marx advocated a living income with "to each according to his needs." Okay, the political right is definitely anti-Marxist on this principle.
But Marx and Engels; despite their advanced educational degrees and finely honed intellects, never asked the most-fundamental question: If these two systems (communal society and technological economy) could be compatible, why did they not evolve together? The only logical answer is that they can't be compatible and the failure of the Soviet system proved that. Soviet leaders openly admitted that they were not practicing pure Marxism because they were surrounded by capitalist enemies and Marxism couldn't flourish until the enemies were vanquished. That was a copout; they didn't practice pure Marxism because they knew it wouldn't work. China abandoning Marxist economics while keeping a police-state society also shows that Marxism isn't compatible with modernity.
Marx never advocated a police state. He lived in a society in which everything was controlled by the propertied and monied classes, a totalitarianism of the bourgeoisie. Government, commerce, the legal system, the church, education were controlled by the ruling ownership classes to serve only those privileged classes. Marx envisioned a system in which those institutions would be controlled by the working classes and would serve the working classes; a "dictatorship of the proletariat." He only envisioned a reverse of the prevailing social order; not the brutal police state the Bolsheviks imposed on Russia and its fellow socialist republics. The society he inhabited differed little from the society in which America is saddled with today except that in his 19th Century, the aristocracy admitted that it was an aristocracy. America's democratic republic and other such nations managed to overcome the ills Marx railed against without becoming totalitarian states by building a strong middle class; that is, until the neo-con revolution beginning with Ronald Reagan began reversing the progress to form what we today know as "corporacracy".
The author is qualified to discuss this matter by virtue of involvement in the US intelligence community defending the nation from communism and studying Marxist philosophy at Georgetown University Graduate School of Government to enhance his employment at the National Security Agency.
While at Georgetown, virtually the entire class came to realize that communism ~ as practiced in the Soviet Union ~ would fail if it were not radically altered. When Mikhail Gorbachev attempted to reform the system, it failed.
The intelligence community felt that containment, not confrontation, was sufficient because it also could see communism self-destructing.
"There comes a time when even speech loses its constitutional immunity ... When conditions are so critical that there will be no time to avoid the evil that the speech threatens, it is time to call a halt ... The restraint to be constitutional must be based on more than fear, on more than passionate opposition against the speech, on more than a revolted dislike for its contents. There must be some immediate injury to society that is likely if speech is allowed."
In that case, American communists were appealing their convictions for organizing study groups to teach their beliefs with the aid of four books: "Foundations of Leninism by Stalin" (1924), "The Communist Manifesto" by Marx and Engels (1848), "State and Revolution" by Lenin (1917) and "History of the Communist Party of the Soviet Union" (1939). There was no question about legality of the books; they weren't, and couldn't be, restricted. Only the communists' speech was involved because a foe of Marxism could have used the same books to teach opposition to communism without fear of arrest.