Well, in my estimation, Roman attitudes towards Christ-believers highlight the incommensurability between Christ-devotion and Roman religion, especially in relation to the imperial cults. The Christ-believers who were persecuted under Nero in the mid-60s CE, including the probable executions of Peter and Paul, were motivated by complex factors. It is certainly true that abstention from the imperial cult is not treated as the reason for the Neronian persecution in any of our sources. What we do know from Tacitus is that Christ-believers were despised for their “abominations,” as a “mischievous superstition,” they were typical of things “hideous and shameful” that make their way to Rome, and for their “hatred of mankind.” Similar criticisms were said of many eastern rites that had come to Rome, both Judaism and the Bacchus cultus, so why the focus on the Christ-believers in the Neronian persecution?
Most likely Christ-believers were singled out because they were regarded as committing national apostasy. By abandoning and even critiquing Roman religion they were religiously impious and politically disloyal. While Roman religion was pluralistic, it was not necessarily tolerant towards foreign cults, especially if they were thought to promote debauchery and disorder. For a Roman resident to profess faith in Jesus as an alternative to Roman religion lent itself to accusations of atheism and hatred of the human race, and was interpreted as a rejection of the mos maiorum (ancestral customs) and committing maiestas (affronting the majesty of Caesar). Neglect of local deities and civic religious duties, especially those sponsored by imperial patronage, amounted to a charge of atheism. This lack of devotion could hardly go unnoticed because it would be conspicuous by its absence from family shrines, from non-participation in religious rites in associations, and from non-attendance at public festivals. Certainly by the early second century, the profession by believers that “Jesus is Lord,” carried with it the seeming impossibility of Christ-believers ascribing the same title to Caesar and worshiping his image, even upon the threat of death as famously demonstrated in Pliny’s persecution of Christians in Bithynia and in the martyrdom story of Bishop Polycarp. Similarly Tertullian wrote how Christians faced “the accusation of treason most of all against Roman religion.” Failure to offer sacrifices and respect imperial images is precisely the accusation brought against Christians by the pagan critics Caecilius and Celsus.
Although much of the evidence discussed derives from the second century, Christian antipathy to the imperial cults most probably goes back to the first century. It was impossible to ignore the imperial cults, since Herod the Great had ringed Judea with temples to Augustus before the time of Christ and Caligula and Nero were resolutely active in cultivating divine honors during the time of Paul. Yes, the imperial cult was merely one facet of Roman religion, enmeshed beside and within other cults. Yet Donald Jones comments: “From the perspective of early Christianity, the worst abuse in the Roman Empire was the imperial cult. Honors which should be reserved for God alone could not be bestowed on men.” The exclusive Christ-devotion of the early church could not absorb veneration of the Emperor and by refusing to participate, Christians were perceived to cut the chords that held politics, pantheon, and people together as the fabric of social cohesion. Viewed this way, Christ-believers were persecuted because they neglected what some thought necessary (worship of the gods), their meetings broke down the social orders between the classes (hierarchies of power and privilege), they promoted controversy and clashes among Jewish communities (a threat to peace), and they abhorred precisely what many adored (Roman power and its benefactions). An analogy can be found with an inscription testifying to the prosecution of Cn Calpurnius Piso in 20 CE on the grounds that “It was also the opinion of the senate that the numen of the divine Augustus was violated by him [i.e., Piso] in that he withheld every honour that had been accorded to his memory or to those portraits which were [granted[ to him before he was included in the number of the gods” Certain Christ-believers refused to place themselves within the matrix of relationships between the gods, the emperor, civic elites, and people, and displaced themselves from humanity’s place in the world in the shared Roman understanding. Thus Christ-believers were not randomly chosen for Nero’s scapegoating among many superstitious cults that had blown in from the east, rather, the non-Roman nature of their devotion, the counter-imperial nature of their discourse, and the anti-social nature of their meetings, probably brought them to the attention of authorities.
 Eusebius, Hist. Eccl. 2.25.5-8.
Tacitus, Ann. 15.44.
Compare Livy, Hist.39.8-19 and Tacitus, Hist. 5.5. See discussion in Mikael Tellbe, Paul Between Synagogue and State: Christians, Jews, and Civic Authorities in 1 Thessalonians, Romans, and Philippians (ConBNT 34; Stockholm: Almqvist & Wiksell, 2001), 26-35.
See Pliny, Ep. 10.96.2; Mart. Pol. 9.2; Tertullian, Apol. 24.1; 28.2. Note that Trajan’s reply to Pliny reveals a “Don’t ask, don’t tell” policy about Christ-believers, but if they are found, then they must be punished unless they recant by “worshipping our gods.” See John Granger Cook, Roman Attitudes Toward the Christians (WUNT 261; Tübingen: Mohr/Siebeck, 2010), 89-92, 290-93. Barclay (Pauline Churches, 359-61) notes that refusing to worship the Roman gods was the point of contention and he regards failure to participate in the imperial cult as only one facet of the “atheism” of Christians. The problem I have is that the imperial cult – not the cults of Roma, the Capitoline triad, nor local cults like Artemis, Serapis, or Diana – was always the litmus test of loyalty. So while the imperial cult might not necessarily have been the primary mode of idolatry critiqued by Paul, even so, Roman officials always insisted on devotion to the imperial cult as a way of unmasking the atheism of Christians and this implies the imperial cult’s prominence within Roman religion and its prominence among those critical of Roman religion. As Wright (Paul and the Faithfulness of God, 1313-14) puts it: “Yes, the Christian refusal to worship the gods in general mattered; but Caesar was always the particular case.” Similar is Bertschmann (Bowing Before Christ – Nodding to the State? 88 n. 39) who accepts Barclay’s point that imagining a Christ vs. Caesar slam-fest is misleading but notes: “Still, I suggest that when the head of political powers orders his Christian subjects to commit compromising actions it can be easily imagined how the confession ‘Christ is Lord’ takes a sharp, polemical ring over against ‘Caesar is Lord’. Caesar then usurps Gods’ prerogatives not just by virtue of presenting himself as divine but claiming the ultimate power to tell people how to live.”
Cicero (Leg. 2.19) said of his ideal state that there “no one will separately have gods, either new or alien, unless accepted by the state.” Cassius Dio (52.36.1-2) presents a speech with Maecenas counsels a young Octavian with the charge: “Those who attempt to distort our religion with strange rites, you should abhor and punish not merely for the sake of the gods (since if a man despises these he will not pay honour to any other divine being) but because such men, by bringing new divinities in place of old, persuade many to adopt foreign practices from which spring up conspiracies, factions and cabals which are far from profitable to monarchy. Do not, therefore, permit anybody to be an atheist or sorcerer.”
 Pliny, Ep. 10.96.1-10; Mart. Pol. 8.1–12.2. We should note that saying “X is Lord” like “Serapis is Lord” as we find papyri does not necessarily imply that “Caesar is not.” Tertullian (Apol 34.1) could say, “For my part, I am willing to give the emperor this designation [“Lord”], but in the common acceptation of the word, and when I am not forced to call him Lord as in God’s place.” The polemic only emerges when a rivalry develops between two apparent Lord’s both described with superlative status and ascribed with unsurpassed authority.
 Tertullian, Apol. 24.1; Pliny, Ep. 10.96-97.
 Minucius Felix, Octavius, 5-10; Origen, Contra Celsus, 8.55-67.
On the imperial cult in Palestine, see James S. McLaren, “Jews and the Imperial Cult: From Augustus to Domitian,” JSNT 27 (2005): 257-78; idem, “Searching for Rome and the Imperial Cult in Galilee: Reassessing Galilee-Rome Relations (63 B.C.E to 70 C.E.),” in Rome and Religion: A Cross-Disciplinary Dialogue on the Imperial Cult, eds.J. Brodd and J. L. Reed (Atlanta: Society of Biblical Literature, 2011) 111-136; Monika Bernett, “Der Kaiserkult in Judäa unter herodischer und römischer Herschaft: Zu Herausbildung und Herausfoderung neuer Konzepte Jüdischer Herrschaftslegitimation,” in Jewish Identity in the Greco-Roman World, eds. J. Frey, D.R. Schwartz, S. Gripentrog (AJEC 711; Leiden: Brill, 2007), 219-51; Werner Eck (ed.), Judäa – Syria Palästina: Ein Euseinandersetzung ein Provinz mit römischer Politik und Kultur (TSAJ 340; Tubingen: Mohr/Siebeck, 2014).
Donald L. Jones, “Christianity and the Roman Imperial Cult,” in ANRW, II.23.2, eds. H. Temporini and Wolfgang (Berlin: Walter de Gruyter, 1980), 1023. See Tertullian, Apol. 27; De Idol. 15; Clement of Alexandria, Oct. 10.2.
 Cited in Koortbojian, Divinization of Caesar and Augustus, 156.
According to Steven R. G. Price (“Ritual and Power,” in Paul and Empire: Religion and Power in Roman Imperial Society, ed. R.A. Horsley [Harrisburg, PA: Trinity Press International, 1997], 71) the imperial cult was “a major part of the web of power that formed the fabric of society” and for Barclay (Pauline Churches, 355-56): “[T]he worship of the divine Augustus (and Roma) indicated the recognition that the imperial order was the guarantor and mediator of the favour of the gods, and that Roman emperors, with their unique and superhuman capacities, were endowed with divine powers to benefit society … One did not choose between worshipping ‘the gods’ and worshipping the imperial house; one worshipped the imperial house because of its central role within the cosmic order sponsored and sustained by the whole panoply of gods.”