The biggest howler here is identifying as a "heritage American", which inevitably means "I'm descended from ppl who were here at the Founding and that's the only thing about my life I can pretend to be proud of, so I hold it over everyone else and demand to be able to rule them."
It's not 'scientific' racism at all--although they usually subscribe to that as well. It's a very specific kind of bigotry (including racism but broader than it).
Literally "my ancestors got theirs and I've got mine and I hate that you've got yours."
In that case you might want to bring to their attention that the stone age tribes that lived in Europe were dark skinned, they DNA profiled some bones, alas no 'glorious, ancient white tribes' for them
We basically recent mutants :P
Other fun fact:
Lots of Nazi occultism and 'white Atlantic master race' crap can be directly traced back to Victorian archeologists salty brown people could build the pyramids
