He writes:

I am debating a whole slew of Protestants, so I was reading your excellent article here.

The first myth you debunk is this:

"The deuterocanonical books are not found in the Hebrew Bible. They were added by the Catholic Church at the Council of Trent after Luther rejected it."

You conclude that this is false because:

"The Septuagint, complete with the deuterocanononical books, was first embraced, not by the Council of Trent, but by Jesus of Nazareth and his Apostles."

In my oppo-research, I came across the disappointingly convincing article here.

Here, the author directly addresses your conclusion, quoting William Weber:

"Josephus not only gave the precise number of the canonical books but stated that the Jewish nation recognized these twenty-two alone as canonical. What is important about his testimony is that he used the Septuagint version of the Old Testament. Thus, even though he used the Greek version, he cited the limited canon of the Hebrews. And as mentioned earlier, Philo also used the Septuagint and did not include the Apocrypha as authoritative canonical Scripture. These cases demonstrate that it does not follow that those who used the Septuagint accepted an expanded canon, in particular, Jesus and the apostles."

Do you have any thoughts on this objection?

My response is that the whole notion of Jesus and the apostles having  a "canon" of Scripture is anachronistic.  It's like talking about whether Beatles were punk or prog rock.  The categories did not exist in their time because the questions driving the need to settle those questions had not yet been asked.  The question about which books could and could not be used in liturgy had not gained force or urgency yet.  Various Jews had various constellations of books they regarded as more or less authoritative.  Some books were agreed on by all while other books were accepted by some and not by others in Jesus' day. Sadducees tended to only regard Torah as inspired.  That's why they rejected the prophets' notions about the resurrection and challenged Jesus' (and, by the way, the Pharisees) teaching on the resurrection of the body.  For them, only Torah was inspired.  So Jesus (significantly) answers them from Torah in the passage about the Burning Bush.  He meets them where they are rather than tries to get them to accept the inspiration of the prophets.

Meanwhile, other Jews have other collections of inspired books.  The proof of this is the existence of the Septuagint itself.  Why on earth do the translators include the books they do if they do not think them to be holy books?  That's the whole reason for the collection the first place: because the translators believe them to be inspired by God, worthy of preservation and dissemination to the Jews of the Diaspora, and worthy of use in liturgical celebrations.  But of course, not all Jews everywhere agree with the translators.  But so what?  There is no authoritative body to decide the question--until the Church is founded and (several centuries later) takes up the question.  Josephus and the Jews he has in mind (that is, the surviving Pharisees and Temple priests after the destruction of the Temple) have their opinion (an opinion not shared by Ethiopian Jews who *still* use the Septuagint).  But that's all it is: opinion.  Josephus is not an authority, nor are the post-Temple Jews.  Because the authority has now passed from God incarnate to the apostles and bishops of the Church.  And they will not really take up the question in a formal way till the late 4th century. They use the Septuagint for the same reason Josephus does: so that Gentiles who cannot read Hebrew can know what the text they are quoting says.  But neither Jesus and the apostles (nor their Jewish contemporaries are making any particular point about whether books should be taken out of or left in the Septuagint.  It's not under discussion.  When it does come under discussion, that will be long after the founding of the Church and the divergence of Church and synagogue.  And precisely the question of the community's relationship with the Gentiles will be a major driver in prompting Israel to adopt a somewhat different canon than the Church. Significantly, that question will involve a project undertaken by Pope Damasus to regularize the liturgy of the Church in union with that of the Roman Church.  The canon of Scripture is nothing more or other than "the books we read during the liturgy": Ie. the Septuagint, which the Church has never had any particular reason to edit.  Jerome, having lots of contact with Jews and Jewish opinion and scholarship about the content and text of the Old Testament was of the opinion that the Catholic canon should match that of the Jewish community in Jerusalem.  But that was also merely his opinion.  Holy Church thought differently.

Bottom line: appeals to the opinion of Josephus and of the community in late first century Judea don't tell you anything other than what their opinion was.  Meanwhile, the practice of the Church was to use the Septuagint in its readings.  Eventually, that practice is ratified by the Magisterium of the Church in the late fourth century and (at Florence and Trent) that practice is made dogmatic.  Appeals to the opinions of a Jewish community that, by the time Josephus was writing, had already split with Jewish Christians and had a deep animus to both the Church and the Gentile converts to whom she read the Scriptures in Greek only tells you that, yes indeed, there was a real and hardening divergence between believing and unbelieving Jews.  It tells you nothing about which books belong in the Bible.  Only the Magisterium can do that--and did.