False equivalency, The Lords Aymeric, Artoriel, and Edmont discovered the truth behind a thousand year war of survival and immediately worked to let the truth be known. Though I would gladly swing the axe for the people if they so choose. I'm not exactly married to the idea of keeping titles of Nobility and the holier than thou mentality as I personally dislike it in real life.
Gaius on the other hand is a war criminal and known tyrant and slaver. The men of Ala Mhigo were put to hard labor and the women were made to do "far worse". Policies I'm sure that would have carried into the rest of Eorzea had he not been stopped at Silvertear. That's your preferred ruler? Gaius "adopt them to bop them" Van Baelsar? Who knowingly worked with an Ascian as a tool to his detriment. Fine, I will throw out another alternative, imprisonment and a trial. Nuremburg style. Again, I would volunteer to swing the axe. I only say this due to your comment about Rome being the framework of Garlemald. So corruption, heavy handed policies, and weak leaders. Yeah, that matches up. Why reward them?
Nerva? lol
Neither do the losers of a war they started.
I'll grant you that the Garleans were bullied early on. But until evidence is given otherwise? I'm going with the Ascians creating a slave race with a chip on it's shoulder to instigate a war and cause mayhem the world over to make the beast tribes summon primals to justify expansion to create more conflict to create havoc... etc. etc.