For Karl Marx, religion was “the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. [And] the opium of the people.” For Marx, as for socialism and communism later on, religion was absolutely against everything that they stood for. Where communist regimes established themselves, religious people were ruthlessly oppressed.
In the USSR, Christian priests were arrested, and physically and psychologically tortured.In Maoist China, and its “Cultural Revolution” in which the nation’s traditions and culture were attacked and destroyed, Buddhist monasteries were closed down, and Buddhism, Christianity and Islam were oppressed.

A Buddhist monk looks at a painting by Vann Nath. It shows Khmer Rouge guards torturing a prisoner with whips.
Communism was responsible for as many as 100 million deaths during the 20th century, says Lee Edwards in his Collapse of Communism, published by the Hoover Institute.

“We can all share the same star”: A painting by Vann Nath depicting a prisoner being tortured under Cambodian communist regime.
Recent political events, suggest that the strategy of neo-Marxists and similar extremists, is to transform the religions into political constituents in a game of identity politics. This will see the faiths stripped of their timeless values, and used as the hollowed out puppets of political whim.
The cynical and sinister European Union poster has only recently come to light. Notably the religions are all presented as being within a single star. The EU emblem is a circle of 12 stars, although one of the major, and most recognizable, communist emblems was a five pointed star.
At the pinnacle of the large star, comprised of different religious symbols, in the EU poster, is the hammer and sickle, the main symbol of communism, under which the religions have traditionally been attacked and oppressed. This image also appeared in Arts and Visual Communications by Sladjana Zunic, Sladjana Bajic, Anke Gardasevic and Helichrysum Vukicevic, an EU textbook published in 2010. However, while the communist hammer and sickle appears alongside religious emblems, in this version the Islamic crescent and star is at the pinnacle of the main image. This has subsequently been replaced by the communist sign.










Marxism is a religion like any other, and should be addressed as such. There are polytheistic religions, monotheistic ones, and atheistic ones, like Marxism and also the two main Chinese traditional religions, Confucianism and Taoism, and maybe it is the reason Communism is still the dominant ideology there. The fact you allege as to Communism’s having suppressed all traditional religions (except judaism, out of which it derives as an atheistic version) within its pale proves nothing irreligious about it: wherever Christianity is politically dominant, it persecutes both all other theistic faiths and communism.
On the contrary, while there is a relatively broad spectrum of religion, the one essential and defining factor is that religion is orientated toward the transcendent, or at the very least believes that there is a transcendent, e.g., a god, supernatural force, life after death. (You might argue that Zen Buddhism is atheistic, but this is only true if one adheres to a strict Christian, or at least strict monotheistic, worldview, since Zen has a notion, or notions, of the transcendent, from Chi (subtle energy) to reincarnation, not to mention its reverence for Buddhas and Bodhisattvas.)
Communism, on the other had, claims to be a materialistic science, and, as such, rejects any belief in a transcendent. It is concerned with creating a particular type of society, and human being, on earth. Moreover communism regards religion — in the words of Marx — as “the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions. [And] the opium [i.e., pleasing but incapacitating illusion] of the people.”
Communism does of course owe a debt to Christianity (most obviously to the idea of equality, a concept that is Christian and post-Christian in the formulation as we tend to understand it) and, perhaps also — as you say — Judaism. But, it has secularized these ideas, and made them part of an entirely materialistic worldview.
I’m not sure Confucianism — which you also mention — can really be described as a religion either. It is an ethical system, concerned with creating the harmonious society, and encouraging the cultivation of man through the classical Chinese arts (including ritual).
In regard to violence, there is no doubt that most religions have committed horrible acts of violence, sometimes on a relatively large scale — and that includes Christianity. But there is something perverse and disingenuous about including a self-professed materialistic science, opposed to religion, along with the religions themselves.