they were quite devout Zoroastrians, rather dedicated to killing the Christian Romans. It seems to me the Iranians I know aren't privy to that fact. They just claim their ancestry to be Christian.
Could it be that their enemy bent on slaughtering them just happened to be Christian also?
From what you said Rome was the aggressor, the guys who decide they wanted someone else's space. Not sure why you would blame the Iranians / Persians for this. Right now we are scrambling and praying to protect our own little plot on this planet from aggresors.
I really don't know. Someday I'll work on googling this conundrum but any links you can provide to support your assertions would be appreciated.
"But the present-day Persians have almost completely abandoned their old ways [...] ever since they have come under the spell of the doctrines of Zoroaster the son of Ahura-Mazda" The historian Agathias, wrote this in Constantinople in the 6th century CE. The source is from "Readings in Late Antiquity," edited by Michael Maas. And it simplifies the situation too much to say that either the Roman or the Persian power was the aggressor. They were essentially at constant war for four hundred years, both after power and territory. I wasn't blaming either side; rather, I was just saying that Persia wasn't actually Christian.