Best way to demoralize your enemy? Take their women, separate them, and make the men watch as you treat them like cattle. It makes the other side feel powerless, and it wouldn't surprise me if the female commanders encouraged it; it certainly doesn't mean they wouldn't participate to help the cause along, either. Women are generally easier to control compared to their male counterparts. Even by Eorzean standards, women are smaller, including Roes, though I suspect they probably put the female Roes to work as well, given their size.
Rape demoralizes both genders, even if they only take the women. Female soldiers feel demoralized and humiliated, just the same as the female civilians, and the men are helpless. It's not about sexism, or gender equality, it's about control and keeping the enemy down. It also encourages young male soldiers, as a bonus for signing up.
Edited to add: There's one more point, there's only one of the two genders capable of having babies. The conquering army doesn't care if they're bastard children, they want more canon fodder.
Rape demoralizes both genders, even if they only take the women. Female soldiers feel demoralized and humiliated, just the same as the female civilians, and the men are helpless. It's not about sexism, or gender equality, it's about control and keeping the enemy down. It also encourages young male soldiers, as a bonus for signing up.
Edited to add: There's one more point, there's only one of the two genders capable of having babies. The conquering army doesn't care if they're bastard children, they want more canon fodder.