Christianity was the Communism of Antiquity

Christian theology is the grandmother of bolshevism. 
-Oswald Spengler, The Hour of Decision. 1933.
"The history of early Christianity has notable points of resemblance with the modern working-class movement. Like the latter, Christianity was originally a movement of oppressed people: it first appeared as the religion of slaves and emancipated slaves, of poor people deprived of all rights, of peoples subjugated or dispersed by Rome. Both Christianity and the workers' socialism preach forthcoming salvation from bondage and misery; Christianity places this salvation in a life beyond, after death, in heaven; socialism places it in this world, in a transformation of society. And in spite of all persecution, nay, even spurred on by it, they forge victoriously, irresistibly ahead. Three hundred years after its appearance Christianity was the recognized state religion in the Roman World Empire." 
-Frederick Engels.
"Marxism borrows some deep assumptions from theology, especially its prophetic criticism of the present world order (capitalism) and its eschatological projection of a future world that is qualitatively different. It is not so well known that when Marx and Engels wrote the Manifesto of the Communist Party they did so at the request of a group that had not long beforehand been known as the League of the Just. The curious thing about the League of the Just, which had been formed by German workers in Paris in 1836, was that it was an organisation with a substantial religious flavour, propagating utopian socialist and communist ideas and practices on the basis of the Bible. Some of the leading figures of the old League of the Just argued for a violent communist revolution and pictured not merely Christ as the fore-runner of communism, but communism as Christianity without all its later developments. If a religious person declared she or he had become a socialist, then the assumption is that that person had lost his or her faith. It doesn’t help matters when the major churches also declared communism to be ‘God-less’. But these are, or at least should be things of the past." 
-Roland Boer.
This may result contradictory to many people, because communism is an atheistic and materialistic movement, but the fact is that "New Testament" reveal ideas that are in communion with Marxists thoughts like its ostensible "egalitarianism" which says that "All are children of God". Paul, the "Apostle of Gentiles", says very clear that there is no race, no class and even no gender for those who believe in Jesus as "Son of God":
"There is neither Jew nor Gentile, neither slave nor free,  nor is there male and female, for you are all one in Christ Jesus".
- Galatians 3:28.
 "And all that believed were together, and had all things in common; And sold their possessions and goods, and parted them to all men, as every man had need". 
-Acts 2: 44, 45. 
"And the congregation of those who believed were of one heart and soul; and not one of them claimed that anything belonging to him was his own, but all things were common property to them". 
-Acts 4:32.
"For there was not a needy person among them, for all who were owners of land or houses would sell them and bring the proceeds of the sales and lay them at the apostles' feet, and they would be distributed to each as any had need. Now Joseph, a Levite of Cyprian birth, who was also called Barnabas by the apostles, and who owned a tract of land, sold it and brought the money and laid it at the apostles' feet." 
-Acts 4:34-37.
For the kingdom of heaven is like unto a man that is an householder, which went out early in the morning to hire labourers into his vineyard. And when he had agreed with the labourers for a penny a day, he sent them into his vineyard. And he went out about the third hour, and saw others standing idle in the marketplace, And said unto them; Go ye also into the vineyard, and whatsoever is right I will give you. And they went their way. Again he went out about the sixth and ninth hour, and did likewise. And about the eleventh hour he went out, and found others standing idle, and saith unto them, Why stand ye here all the day idle? They say unto him, Because no man hath hired us. He saith unto them, Go ye also into the vineyard; and whatsoever is right, that shall ye receive. So when even was come, the lord of the vineyard saith unto his steward, Call the labourers, and give them their hire, beginning from the last unto the first. And when they came that were hired about the eleventh hour, they received every man a penny. But when the first came, they supposed that they should have received more; and they likewise received every man a penny. And when they had received it, they murmured against the goodman of the house, Saying, These last have wrought but one hour, and thou hast made them equal unto us, which have borne the burden and heat of the day. But he answered one of them, and said, Friend, I do thee no wrong: didst not thou agree with me for a penny? Take that thine is, and go thy way: I will give unto this last, even as unto thee. Is it not lawful for me to do what I will with mine own? Is thine eye evil, because I am good? So the last shall be first, and the first last: for many be called, but few chosen. 
— Matthew 20:1–16.

Even when Marxism is opposed to religion, including Christianity because it represents to it certain "traditional values" and "spiritualism", if you remove all spiritual and metaphysical concepts from Christianity, what you get is a form of Marxism. Being atheistic, Marxism doesn't accept the metaphysics of christianity, but it's nurtured by all its ethics: Marxism is the secularization of Christian theology. Furhtermore, actually both movements have shown sharing a common operation and historical features:
  • Both have a core of unprovable beliefs.
  • Both share egalitarianism and universalism, i.e. a doctrine that want a world without borders, races, nations or ethnic groups. This is catholicism (small c) for the church, and internationalism for socialists.
  • Both hope for a “future kingdom of justice and freedom”, an Utopia of peace and fraternity among all humankind.
  • Both assign great value to community, to “communal life”, to the “communal sharing of goods”.
  • Both consider the poor to be victims of injustice. Both first seek to draw attention to the lower strata of society to preach their “message”, and historically, both reached power through the rebellion of the lower classes against the higher classes.
  • Both had institutions checking that nobody has any actions, thoughts or words against the doctrine (The Inquisition and The KGB) - anyone breaking their rules will go to stake or gulag. While religions were oppressed and arts were severly regulated in soviet world, Christians of fourth century started large-scale religious persecution aimed at eradication of all non-christian religions and destruction of all temples. This was a Christian innovation (except it was inspired by Judaism, of course).

Indeed, before that, the Roman empire only made limited persecutions of the Christians, and these were essentially political, not religious, and were justified by the threat posed by Christianity to the Roman society. The Roman Empire always tolerated different religions, but their authorities saw in Christianity a subversive sect of an anti-Roman preaching. Rome simply acted in self-defense against this poisonous anti-Roman threat, with no purpose to exterminate them.