Well, they did get their butts kicked by the vikings, so maybe that hatred has been passed down.
The Scots have the highest percentage of red heads in the world.
My Brother told me it was the Irish so I looked it up. Lots of famous red heads in history. King David, Ramses The Great, Andrew Jackson, Thomas Jefferson, and on and on.
And Saxons. The ginger gene was probably well-represented among the Saxons.