Although ethno/racist prejudices were common in Greek/Roman societies, there was no systematic persecution of any specific group (Isaac).  Nevertheless, the Gentile Christian message rejecting association with Jews and Jewish laws would have found a willing audience among Greeks and Romans who shared disdain for Jewish practices such as male circumcision, refusal to eat pork, and refraining from labor on the Sabbath.  According to Barclay (1996), such Gentile hostility was also abetted by Jewish "exclusivity" (p. 272) including Jewish opposition to "idolatry" (p. 274), fears "that the Jewish community was of influence and importance—perhaps growing importance—within the life of the city" (p. 276), and "their social cohesion—a feature which malevolent observers would interpret as clannishness or misanthropy" (p. 287).  Barclay lists other "faults" and "contrary" practices ascribed to Jews by Roman writers such as Tacitus (ca. 110 C.E.) including their increase in numbers caused by Jewish "lust," and their "refrain from intercourse with foreign women" (p. 411).  Goodman (1987, p.61) notes that the absence of Jewish infanticide and abortion also generated Tacitus' "amused contempt."

Since there was no connection to "Jew" in the Greek appellation "Christian," its first century adoption by Antioch Christians (Acts of the Apostles 11.26) and St. Paul's adoption of the name (Ibid. 26.28–29) would have removed Christians from the status of being solely a Jewish sect.  By the year 100 C.E., St Ignatius already defined Gentile Christianity as uniquely distinctive: "It is absurd to speak of Jesus Christ with the tongue, and to cherish in the mind a Judaism which has now come to an end.  For where there is Christianity there cannot be Judaism" (Letter to the Magnesians X, ANF vol. 1, p. 63). 

"The name 'Christianoi' (Acts 11.26…) is an unmistakable indication that the Church has detached itself from the synagogue.  With this step it had freed itself from the obligation to observe Jewish purity laws and the circumcision commandment but had also placed itself outside Judaism and affiliation with the people of salvation [Jewish Jesus-followers — 'Nazoreans']" (J. Becker (p. 147).  "[W]hat was distinctive about such communities that might explain why they in particular were marked out by the authorities as a recognizable, and therefore namable, group was precisely that they comprised former 'pagans' rather than Jews" (Townsend, p. 219).

Use of the name "Christian" thus marked both a religious and ethnic separation in "Parting of the Ways" between early Gentile Christian and Jewish communities, whether or not the latter were Jesus-believing.  That is, religious, cultural, and ethnic features which distinguished Gentile communities from Jews also distinguished St. Paul's Gentile Christian churches from Jewish Jesus-believing synagogues. "In social reality Paul's churches were distinct from synagogues, and their predominantly Gentile members unattached to the Jewish community" (Barclay 1996, p. 386, also Esler 2015).  By the second century, Christian writers "self-consciously use the term 'Christian' for insiders, portraying this membership in terms of descent and kinship as well as transformation" (Kimber Buell, p. 183).