At this point I think just about everybody has seen the South Park episode where Cartman becomes the leader of an "anti-ginger" hate group, and explains to his followers that "Gingers have no souls." When I saw the episode, I was convinced that Trey Parker and Matt Stone made the whole thing up in order to build an episode around the most ridiculous hate group imaginable. But then, I recently came across this article, which claims that there is in fact a long tradition of prejudice against redheads, dating back to ancient times.
During the Middle Ages, a child born with red hair was thought to have been conceived during ‘unclean’ sex, or during menstruation.
In ancient Egypt, redheaded men were sometimes burned alive as a sacrifice to the gods.
Redheads were particularly persecuted during the witch trials in Europe between the fifteenth and seventeenth centuries, as the colour was linked to the devil and the pale skin most redheads have was seen as deathly and unnatural.
Even though grimoire traditionalists will tell you that the older an idea is, the more likely it is to be correct, it should be obvious that this one is clearly pretty dumb. Much like the ludicrous African idea that the body parts of albinos have special magical powers, there's nothing particularly infernal or for that matter magical about having red hair. In fact, I can't say that I've ever come across any evidence that traits like hair color correspond to anything spiritual at all, one way or the other. The same is true of ethnicity.
The reality is that if you are talking about genetic variation, the differences between individual humans are tiny compared to those found between individuals of many other species. A little over a hundred years ago, Theosophists developed a complex metaphysical theory involving "the races," but at a genetic level, all "race" represents is a set of adaptations to local environmental conditions. Skin gets darker towards the equator to protect against skin cancer, and lighter as you move away from the equator to help the body synthesize vitamin D from limited sunlight.
So amazingly, it turns out that "anti-ginger" prejudice is or at least was a thing. But like most forms of prejudice, it is an ill-informed idea based on superficial characteristics that should be done away with.