Basically the argument seems to be that, if an account of an event, based on whatever historical records exist, is capable of being used to justify oppression and persecution, the right thing to do is to reject this version, and replace it with a different version which is less likely to be used in that way, even if there are no historical records which justify it.

Interesting. I wouldn't wholly disagree, historical records are often very defective - but a revisionist version such as that should always be identified as a speculative and tentative hypothesis.

There doesn't seem anything improbable about the story of the Crucifixion that emerges from the Gospel accounts. It's quite easy to imagine a similar train of events in modern colonial and post-colonial times.