Redheads were thought to be witches.
45,000 red-haired women are estimated to have been burned for witchcraft in 15th century Germany. According to the manual on identifying a witch, Malleus Maleficarum, a sure sign would be her having red hair and green eyes.
I believe redheads have supernatural abilities that some would label as sorcery or witchcraft.
This may signify the importance of the recessive gene. How can they exterminate all redheads when the gene ‘hides’ itself?