Given how the Tusken were always treated prior to The Mandalorian/The Book of Boba Fett as the equivalent of the "savage Indians" in old Westerns, I wonder if maybe Padme just didn't think of them as people, if she had an unexamined prejudice that led her to dismiss their slaughter as unimportant. I mean, it's hard to see how someone belonging to a diverse multispecies civilization would have a racial prejudice, but maybe it's a prejudice based less on species than on civilization, so that she thinks less of a species living at a "primitive" level than one with cities, high technology, etc.
That's hard to reconcile with Padme's character as usually portrayed, certainly in The Clone Wars, but within the context of the prequel trilogy, given the trope the Tusken Raiders embodied in Lucas's films, it kind of fits. And a lot of people have prejudices they don't recognize. Sometimes a person can be very open-minded and inclusive in most respects, but still have one group that they reject and dehumanize. For instance, I recently read a review of one of my books that praised its cast's ethnic and gender diversity but then gave me whiplash by complaining vehemently that the book included a nonbinary character and addressed pronoun preferences.
