How does this "defang" the James passage in the Antiquities? Origen's "misrecollection" isn't the same as what Josephus says. In fact, in War 4.5.2, Josephus says Jerusalem fell because of the death of Ananus.The Antiquities mention is fairly straightforward to defang, because it so obviously depends on a misrecollection by Origen which was accepted by Eusebius and Jerome. Centuries passed, and by golly, the Origen-Eusebius-Jerome version became the only version there is.
I should not mistake if I said that the death of Ananus was the beginning of the destruction of the city, and that from this very day may be dated the overthrow of her wall, and the ruin of her affairs, whereon they saw their high priest, and the procurer of their preservation, slain in the midst of their city. He was on other accounts also a venerable, and a very just man ...
This sounds more like what Origen could have "misrecollected" than the James passage to me. Compare the above with what Origen says in his Commentary on Matthew 10.17:
And to so great a reputation among the people for righteousness did this James rise, that Flavius Josephus, who wrote the “Antiquities of the Jews” in twenty books, when wishing to exhibit the cause why the people suffered so great misfortunes that even the temple was razed to the ground, said, that these things happened to them in accordance with the wrath of God in consequence of the things which they had dared to do against James the brother of Jesus who is called Christ. And the wonderful thing is, that, though he did not accept Jesus as Christ, he yet gave testimony that the righteousness of James was so great; and he says that the people thought that they had suffered these things because of James.
Perhaps Josephus' description of Ananus as a "very just man" reminded Origen (or whoever he learned the story from) of James. And Josephus also mentions Ananus' death along with someone named Jesus, which could have also confused Origen (or whoever he learned the story from). And Josephus says that this Jesus was "inferior" in comparison to Ananus, which could have given Origen (or whoever he learned the story from) the impression that Josephus consequently "did not accept Jesus as Christ."
And Origen doesn't say he saw his James story in the Antiquities (or anywhere at all), only that Josephus is the guy who wrote the Antiquities in twenty books, which I think supports the idea that Origen (or whoever he learned the story from) "misrecollected" the Ananus passage in the War.