Hard disagree. That's a utilitarian mindset. Morals is relevant regardless of whether the assumptions are faulty.
Even if Hitler had been right, and genociding Jews and Slavs truly was what would bring Germany up, even then, he would have been morally wrong.
You're begging the question here: the ends definitely do NOT justify the means in the case of genocide. That's it. Hitler was a morally bankrupt man not because of his flawed assumptions (we do agree they were flawed) but because he decided genocide was acceptable. Nothing else matters. Genocide is always wrong.
> The immorality of genocide flows downstream from my morals, it's not an axiom
Inasmuch as we are humans and there's no such thing as objective fact, but you're saying is trivially true but also too abstract.
For humans, genocide of other humans is always wrong. Don't sci-fi me, don't insult my intelligence. I have no failure of imagination: there is simply no future scenario where genocide or rape is acceptable, ever.
Genocide is always wrong. Survival at all costs -- say, by murdering children -- is unacceptable. No future scifi scenario you can think of will make it acceptable. It's ok to lose -- not you, humanity I mean -- if we reach such a dead-end where the only possible "solution" is genocide. It's ok to say "we cannot solve this problem, we cannot follow this abhorrent path".
"Your morals, axioms, etc": as I said, I've little patience for moral relativism as an argument for this kind of debates.