(I'll try and cram these into some kind of structure, so be warned: Here Be Lists)

1/ Mary-Sues are of course not defined by their appearance. There are almost certainly millions of blonde/blue characters who aren't 'Sues - and equally many 'Sues who don't have blonde hair! For that matter, what self-respecting 'Sue would have an eye colour as boring as 'blue'? Now, if 'Aryan' meant 'and I mean like with these really vivid purple orbs only when she gets angry they glow red'...

2/ I know you weren't, but let's be careful not to compare 'Sues - or, especially, Suethors - to Nazis.

3/ Hitler, of course, doesn't pre-date fanfiction. Fanfic is ancient. To pick a random (and if you can believe it, relatively modern) example, the Aeneid, by Virgil, is fanfiction of the Iliad - and is over two thousand years old! I'll leave it to someone who's read the thing to decide whether Aeneas is a Gary-Stu...

4/ Coming round eventually to your original idea... what if Mary-Sues existed before they were a common feature in fanfic? What if, indeed, a society on Earth (or a canon world) dedicated itself to breeding them?

A few thoughts:

-The League of Mary-Sue Factories, along with a number of other groups in the Multiverse (there's a city somewhere named Sparklee...), are doing just that: producing 'Sues, one way or another, and sending them into fanfic. The League have used them to attack the PPC on occasion. Sparklee, actually, goes even further - it's set up as a city-state populated entirely by 'Sues and 'Stus, pretty much exactly like you're thinking of.

-For that matter, the Mirror Multiverse Enforcers of the Plot Continuum (EPC) are doing much the same thing - building a society of 'Sues, and attempting to conquer everything else. They're a dictatorship with no regards for morality or ethics, so I'm sure Nazi parallels have been drawn...

-What I'm not sure anyone has written is a society of normal people which - by choice or by external/dictatorial force - turns itself into a nation of 'Sues. It could be an interesting story, indeed - but I wonder how hard it would be? After all, Mary-Sues, by occasional definition, aren't exactly well-rounded characters - and aren't (usually!) intentional villains. Writing a story about 'Sues taking over, while ensuring the 'Sues can keep their own worldview (how they are the best thing ever to happen to everything) intact... it would be a big challenge.

hS

While that might be true, a lot of people would find that demeaning or offending. Here there be dragons, methinks, and it's best not to tread there.