well, lets take the only point of your post which is true:
so, other peoples were enslaved and killed too. I fail to understand how that makes the Third Reich better. Actually, it makes it worse.
I really, really hope that not all those who support the Sith have real life opinions like you do.
the word "killed" makes a difference, they were not intentionally killed, their deaths were a product of a difficulties in a camp, food, hard work, lack of hygiene and many other things - but that was a common practise, I mean camps since history of wars
I justify progress and understand that you cannot avoid victims, if you want to break a spirit of a conquered nation, it depends on culture. Even Sith Empire is not exactly obliged to slaughter everyone, they can simply ask some smaller states to join them, if they refuse, attack them, then ask them, if they refuse, well, that is a beginning of a terror