Well, to make a more serious comment instead of just quoting an old song from an old movie, it's definitely most important to call people by pronouns that they prefer. That's the number 1 priority.
That said, I have some trans friends who don't like gender neutral pronouns in general. One in particular has explained how much she has gone through to be able to identify as a woman, and using "they" instead of "she" makes her feel like she still isn't a woman.
So the real answer is there's no one word that will make everyone happy. They best way to do that is to ask people the pronouns they prefer.
Not disagreeing with anything you said, I just find it mildly amusing when people call things war crimes when they took place before the Geneva convention. There was no international agreement on what a war crime is at that time, so technically nothing was a war crime back then. They were free to commit all the genocide they wanted.