That's rubbish.
I use the written works of Josephus as an account to testify to Christ's historical validity for secularists who want secular proof.
Josephus has a place, but documenting and verifying prophecy is not it.
Sorry.
Translation: "Josephus is useful to defend my opinions, but Josephus is worthless if it means I might be wrong about something."
The real irony here is that I imagine that the portion of Josephus' work you use is going to be the Testimonium Flavianum, something generally regarded, at best, with suspicious by virtually all historians and scholars as a possible late interpolation; but when Josephus simply recounts the abuses of the Romans in their sacking of Jerusalem it cannot be reliable because...
reasons.
Not too long ago I was engaged in a discussion with a Muslim fellow who insisted that St. Paul never existed, claiming there are no valid sources that uphold that Paul ever existed--and said that Paul's epistles were all written in the mid 2nd century by Marcion of Sinope. When evidence to the contrary--such as the writings of the fathers--were given as testimony and evidence of Paul, not least of which being St. Clement's letter written around 95 AD who mentions both Paul and Peter as having preached in Rome, the rebuttal was simply to dismiss these too as forgeries.
The reason for rejecting any evidence was an ideological one, not a rational or scholarly one. The evidence pointed to the historical reality of Paul of Tarsus, and that he is the earliest witness and author of the Christian tradition we have in writing. That is generally regarded as indisputable fact within the scholarly community, secular, religious, whatever. But Paul represented a problem, because if Paul existed, if his letters are authentic and early, then he represents a rather remarkable witness to the beliefs and teachings of the earliest Christian communities that existed; and that those communities were teaching a crucified and risen Jesus, and calling Him "Son of God". That simply does not mesh with Muslim dogma, which insists that Jesus was rescued from death on a cross and taken directly into heaven without tasting death, and is adamant in its polemical confession "God has no son".
If early Christians, as witnessed by Paul, actually did believe Jesus of Nazareth was crucified, buried, risen; and that He is called "Son of God" from the earliest strata of Christian religion, it indicates that Jesus' own immediate followers believed, confessed, and taught these things. That doesn't exactly bolster the Muslim position. Thus if we can get rid of Paul from the picture entirely, that whole problem goes away.
I don't very much see your rejection of Josephus' account of Jerusalem's sacking by the Romans as substantially different. You have opted to dismiss the historical record not out of legitimate criticism of Josephus' credibility as an historian, but because I used Josephus' account as corroboration with Luke's text. Because if Jesus has spoken, and those events have transpired, then it becomes further difficult for you to claim Jesus was not speaking about what transpired during the Jewish-Roman War and to insist on your own particular doctrines over and against the plain reading of Scripture, plain history, and plain reason.
That's an ideological rejection of Josephus, not a reasoned one.
-CryptoLutheran