I have a theory. It has been pointed out that Crowley is much angstier in Rome than before, with hair cut and gloomy mood, and I think it's because now he's being slowly encircled by the Xtian dualistic narrative (bad vs good, don't ask questions, unforgivable, etc). Aziraphale is not so happy himself before he sees Crowley. They are two Jews on the road who catch each other stealthily reciting Shma and exchanging knowing smiles. Crowley is so offended by "let me tempt you" because now their banter gets the whole new meaning, now they are enemies. They have no problems chatting in Eden, by the Ark or at Golgotha. They are genuinely sorry about Jesus, because who wouldn't be. Crowley says "your lot put him up here", and Aziraphale snaps that he's not consulted on policy decisions. Besides, Jesus is another Jew killed by the Romans, and it brings back a lot of unpleasant memories to both of them. They mostly refer to their sides as "my lot", "my people", very rarely as Heaven and Hell. Crowley still keeps kosher in Rome, while Aziraphale went fully Hellenistic. Their sides are not heaven and hell. Their differences are of a religious character. Demons be like, we questioned and argued and the Almighty Rabba got a bit pissed with us so we stormed out and hid ourselves in caves. Angels be like, oh yeah, classic beauty and no eating for pleasure and let's go all ascetic, and let's separate between body and soul etc. Aziraphale is a bad angel, because he is a Jewish angel, joining the Maccabees and being rejected for it, while Crowley is a bad demon because ok, why not stay friends with other Jews over some disputes? We were created to dispute, right? And the Almighty Rabba has been trying to find her lovely students who stormed out like spoiled kids and she made them such fluffy kugel and could they come home and eat and have a discussion and never again leave like that and do you know how worried I was? And while She was looking for them her stickler students remained unmoderated and came up with all sorts of weird opinions and killed a Jew!
That's ma point.