Sheshbazzar

As far as I've been able to determine, in the original the Haaretz article he did not specifically say "Palestinians" it seems that it was the;
that was revised into the AL AHRAM WEEKLY's version of his comment;
"All of the Palestinians must be killed;......the religious opinion issued one week ago by Rabbi Yisrael Rosen.."

The entire civilized (and not-so-civilized) world has seen the pictures of the Palestinian population's dancing in the streets at the inflicting of damages upon Israel,
time and time again, so the connection between what he actually stated, and the people to whom he would be referring is not all that obscure.

Another thing that needs brought out here though, is the problem of language differences, (I have both Jewish and Muslim family, and acquaintances) sometimes in the translating and conveying things from one language into another, or as in this case, where we are reading the accounts of these matters in yet a third language,
The exact sense can become entangled, particularly when it is being interpreted and translated under extreme prejudices.
But the evidence that the gist of Rabbi Rosen's statements were correctly understood, lies in the evidence of how his fellow Jews understood and responded to his comments.

Without going into reciting each individual verse, as it is presented in the texts, it is not just folk memory, but quite detailed accounts that were obviously intended to convey a "history" of actual events, as such, if those related "events" did not actually take place at the time, and in the manner that they are presented as having been done, then they are by definition fabricated accounts of things that didn't actually happen.
Someone had to be responsible for the inventing of, and the providing of these details.
That someone was coming up with a lot of detail that would not be present in any simple "folk memory". If he was working with older documents as his sources and just compiling them, then it just removes it to the older sources as being the inventors of the stories, the end result is still a work of fabrication.
Is killing "enemies" in war considered to be committing murder in the Jewish religion?
In any case, the Jews killing off of the competing peoples of the land would have provided them plenty sufficient rewards and benefits in this world.

Do I think it happened that way? Nope, "Jewish history" before the time of Ezra is something more like 90% make believe, 9% of something must have happened, and 1% of actual "real in this world" history.