That’s not the kind of propaganda he’s talking about. He’s transferring modern ideas - psychological warfare against a whole population - back into the past, where the concept just didn’t exist in the way he’s describing. I’m trying to think of a near parallel. The Romans had grand military symbolism, true. Don’t forget about Napoleon either :). But don’t forget, the Romans abandoned most of this symbolism themselves before they fell. The 6th C. army of Heraclitus in the Eastern Roman empire look almost nothing like the 1st C. Marian army of imperial rome. And don’t also forget, most of the time the reformed Roman army fought itself, not foreigners ^^. It was the Republican army that did most of the expansion.
The Hellenistic kingdoms created a kind of patronage reinforcement model among the Greek city states around the eastern Mediterranean, where after doing some “good deed” the grateful citizens of the city would inscribe in stone around some prominent temple their over-generous thanks for the despot’s intervention in their civic life, declaring feasts for him or her in perpetuity, declaring them to be god-like or actually gods, ect. The Roman’s mostly just kicked ass and took names. Before the Principate Roman interests in the Eastern Med were almost personal, extracting wealth for their personal use back in Rome. It seems hard to grok where this idea that Jesus was a plant would even come from in the Roman world, especially when the default Roman solution was LEGION SMASH.
Just taken as an intellectual conjecture, why would any Romans bother to create this very, over-subtle mythology, and not do the same with the Gauls, Carthaginians, Armenians or Britons? And then, who would be able to write such a thing? Presumably, the only possible one would be a Hellenised, pro-Roman Jew like Josephus is here assumed to be? But then who would read it? Most of the populace was probably illiterate; you’re going to conquer a province by ghost-writing a counterrevolutionary book and releasing into the wild? Eh…