Has there ever been an atheistic argument for why Christianity? I've heard arguments about the "inconsistencies" and "divinity of Jesus" and etc. but I've never seen one that tries to explain why a person would want to be excommunicated from one's own family or synagogue or even to die for a man who was so radical for his time.
Atheists and sceptics have plenty arguments against the existence of Jesus, the divinity of Jesus, the resurrection of Jesus and even arguments that the early Christians were not persecuted. There appears to be a reluctance to accept the four Gospel records and the Acts of the Apostles as historical evidence, although anything written by historians who were not Christians, who had never met Jesus or known him, might be accepted.
There is an argument that the Emperor Hadrian wrote a letter claiming that worshipers of Serapis called themselves Christians. The letter identifying Christians with Serapis-worshipers was supposedly written in AD 134, but the document from which the letter comes, the Historia Augusta has been shown to be a forgery dating to AD 395. Hadrian did not write the letter. https://www.gotquestions.org/Serapis-Christus.html
Perhaps the fact that thousands of Christians were prepared to die for their faith and belief in the resurrected Jesus discomforts atheists and sceptics because it presents a powerful argument for the reality of Christianity.
It is true that those first Christians ran the risk of being made social outcasts, never mind facing imprisonment, torture and death. Why would any sane and rational person risk all for a myth? According to the historical record (The Book of Acts 4:1-17; Pliny’s Letters to Trajan X, 96, etc.) most Christians could end their suffering simply by renouncing the faith. Instead, it seems that most opted to endure the suffering and proclaim Christ’s resurrection unto death.
What makes the earliest Christian martyrs remarkable is that they knew whether or not what they were professing was true. They either saw Jesus Christ alive-and-well after His death or they did not. This is extraordinary. If it was all just a lie, why would so many perpetuate it given their circumstances? Why would they all knowingly cling to such an unprofitable lie in the face of persecution, imprisonment, torture, and death? We have the apostles Paul and James who willingly suffered and died for their testimony about Jesus, a fact which attests to the sincerity of their belief (see The Book of Acts and Josephus’ Antiquities of the Jews XX, ix, 1).
For sceptics who disregard the written testimony of the people who lived with Jesus, who saw him die and then met with him after his resurrection, we have the non-Christian historical accounts of Flavius Josephus, Cornelius Tacitus, Lucian of Samosata, Maimonides and even the Jewish Sanhedrin corroborate the early Christian eyewitness accounts of these important historical aspects of the death of Jesus Christ. Information on the persecution of Christians by Nero and Domitian (who had 40,000 Christians killed in the year 95) in this link: http://www.biblicalcyclopedia.com/P/persecutions-of-christians.html
If anybody can come up with an argument against Christianity, I would be interested to see it.