As a non Christian, I treasure this Pope as an honest man, but this last November, Pope Francis celebrated the feast of All Soul’s with a Mass held in the ancient catacombs in Rome. He was celebrating a myth.
Francis used the location to repeat the story that Christians were persecuted by Rome. The image of mad emperors and bloodthirsty Roman pagans has been part of the Church’s marketing for at least the 1700 years since the Church took over Rome. That image has been used to appeal to poor people living under persecution.
Francis’ story of blood and gore dates to Pope Sixtus II who became a martyr after he and seven deacons were executed for sedition by Emperor Valerian in the mod third century. Ironically, referring to Sixtus as “Pope” in that era is simply nonsense. Sextus was executed about 75 years before Constantine canonized the Roman state under the Church. The blood thirsty Constantine made himself Pontifex Maximus of the new state church.
In Rome, before and after Constantine, anyone claiming to be the supreme spiritual authority was in violation of state law. Such a claim was punished by crucifixion, the penalty for the crime committed by Jesus himself. So, to the Romans of 248, when Sixtus was killed, executing a heretic was simply an act of protecting the state. After the Christians assumed the mantle of high priests, they mercilessly executed “pagans” for denying the divine authority of their church.
Of course the discovery of the catacombs was and is an important tool to make a point. Dr. Wolfred Cote’s wrote in his 1876 Archaeology of Baptism, “During the dark days of 
imperial persecutions the primitive Christians of Rome found a ready refuge in the Catacombs.” Alarmingly Cote’s statement is still cited in some modern Christian books today.
The truth is that Rome was brutal before and after it adopted the cross. Judea was destroyed because of Jewish refusal to pollute the Temple with a statue to the Caesar as God. The fiercest period of Roman persecution of Christians was 303-306 under Emperor Diocletian. That began decades after Sixtus’ death and not in Rome when Diocletian ordered destruction of a church built to near to his palace. Inconveniently for the catacomb myths, that church was in the Eastern empire but in Nicomedia , a small town in what is now Turkey .. a few miles form where Constantine would build his Christian capital.
Hiding and worshipping in secret? Hardly.
For today’s Church, the idea of worshipping in secret offers an opportunity for evangelical propaganda. Pope Francis stated that some still practice their Christianity behind closed doors. Referring to the era of Sixtus II, the Pope said “It was an ugly moment in history, but it has not been overcome.” He went on to claim that there are “many catacombs in other countries where people even have to pretend they are having a party or a birthday in order to celebrate the Eucharist because it is banned.”
The sad truth is that Francis doesn’t have a monopoly on connecting these myths to modern politics. At a talk at Liberty University in January 2016, future president Donald Trump said that “Christianity is under siege.” Sociologist Andrew Whitehead published a paper in 2018 that showed that “voting for Trump was, at least for many Americans, a symbolic defense of the United States’ perceived Christian heritage.” The Christian Post in July 2019 predicts that “persecution is coming” to America. Mike Pence told Liberty University graduates in May that “freedom of religion is under assault.”
There is a combination of truth and myth about the early Christian church and how it became the empire of Rome’s church. A cult becoming the church of the city of seven hills, and as St Augustine would say becoming the city on the hill.
Christians did worship in the catacombs, but not that many were ever executed. By the time of Sextus the Christians were in positions of power within the city of Rome and throughout the empire. At an earlier point and even through the time of Constatine had there been a democratic method of choosing the empires church Judaism may well have been the choice since at least a third of the empire was Jewish. The thing that got Christians and Jews in hot water with Rome was religious and this whole idea there is one god, and no other god but god. If Jews and Chrisitians just also included the Roman gods as in the feasts, and a visit to the shrine ect then no problem, and some Christians and Jews certainly took that option and prayed to the Roman gods as well as the Christian god.
Emperor Vaerlian the II was serious about doing something about those troublesome Christians who just needed to respect the Roman gods like other defeated people under the empire who kept their own gods as well as the Roman ones, even having churches and shrines in Rome. If it was not for those meddlesome Iranian’s perhaps Valerian could have had time to make a difference, but a three or four year program was little more than a speedbump. Those Christians were good at making babies and conversions. (Not to mention that Christianity was cheaper than the Roman religion, just ask Julius Caesar.)