Another observation which I didn't have time to include.
Adrian Goldsworthy, a historian of the Roman Empire wrote "How Rome Fell" recently. His tone and focus are a bit different than say Gibbons or Michael Grant. I got to the point where he mentions some of the early Christian persecutions just a night or two ago. I believe it was Decius following up on Pliny's reports of the 2nd century ...
Anyway, there were remarkable similarities to the approach of the Japanese, but the enforcement was only sporadic. There were symbolic acts of apostacy in public places and targets were offered two or three chances before the shoe was dropped.
Goldsworthy suggested that the Romans saw Christians as a public morale problem in the face of other threats to the Empire ( Eastern enemies, barbarian incursions, plague...). Similar to the Japanese in the film but not with the decade after decade resolve in every prefecture. Not everyone was on the same page as can be inferred by Constantine's position. Evidently he saw more evidence for a Roman civic mindset in 4th century Christians than in the mindset of the Roman Empire's urban masses. Plus they were literate, writing reams ( or the goatskin equivalent) of apologies, histories and debates among themselves. It's hard to get in the mind of the Japanese rulers at the time, save that they didn't like anything that was coming ashore from tthe outside world.