Is Handsome Truth really an Orthodox jew? Was John Minadeo protesting with the Haredi jews in Israel against the conscription law? I think I found compelling evidence.
Liberal humanistic Christians want you to believe that a concept that isn't in the bible is a sin. Either race is in the bible and separation is Godly, or Race isn't in the bible and "racism" isn't a sin.
Personally I believe that "racism" is an extra-biblical concept and separation is Godly.
Either way, this argument is just Presentism, or judging the past with modern values. Racial theories came from natural observation and genetic science, both of which came from God, not "Protestantism". It's easy to apply those concepts to the Old Testament because God literally favored a specific Tribe to make a point.
However, "LE NAZI BAD" is not a theological position.
Father Justinian Burnett of Alabama (ROCOR) has pointed out that numerous racial theories have come about from Protestantism on the "curse of Cain" that aren't supported by the Church Fathers and that Saint Ephrem of Syria says the curse on Cain has to do with what we would call genetic mutations. Nothing about race. The later Protestant racial eisegesis imported 19th-century categories of race and heredity into the text in ways the ancient and God-bearing Fathers of the East and West never did.