It's not just that they were conquered, but then they were defined as uniquely evil for all time, but then the struggle to maintain that and include or exclude

It's not just that they were conquered, but then they were defined as uniquely evil for all time, but then the struggle to maintain that and include or exclude others as similar never ends. Godwin's law wouldn't be a thing if anyone controlled language even in this specific area. People wouldn't to this day casually compare people and groups to Nazis if there was such a thing as controlling people through language. Given your statement that "enhanced interrogation" is still going on, that means from my framing that calling it torture failed to stop it, hence attempts to control it through language failed. You're saying that language allows it to happen, but I would say the correct framing is that doing it and the desire of people to rationalize it allows it to happen. The euphemism being an effect rather than a cause.