Why? Finding certain people seductively attractive in no way precludes regarding them as potentially evil and dangerous. Plenty of pretty young women (and some handsome young men too) were accused of witchcraft and other evil practices back in witch-hunting days.
According to the very amusing book Sex With Kings by Eleanor Herman redheads were thought to be the product of sex when a woman was menstruating.
I have no idea if that’s true or not.
Hm. All my friends from the UK poke fun at gingers. I find it bizarre that red-heads get so much shit over there. “Oh, he’s all right, but I could never date someone ginger.” 
I also find that inexplicable. When I lived in Denmark in the late 80’s, it was still considered very unattractive.
Southpark certainly didn’t invent the word “ginger” as a derogatory term for people with red hair.
It has been around for a long time in the U.K. and Canada, but I had never heard it in American English before South Park popularized it. OED has cites going back to 1825 as a human hair color.
LavenderBlue, I found the same information in Stephen Wilson’s The Magical Universe: Everyday Ritual and Magic in Pre-Modern Europe.
Some Speculation…
People worked outside more before the industrial revolution. They were outside either working the land or doing other labor.
Redheads are extremely fair skinned. They don’t tan and develop protection from sun. Redheads burn, peel, and then burn again. It would be very difficult for them to be outside working 10 to 12 hours a day. Their damaged skin would quickly develop ulcers and probably skin cancer.
I can easily imagine village people labeling redheads lazy and up to no good. “Look at their untended fields! What a disgrace it is. It’s 1 in the afternoon and they are still in the house.”
Or, even worse. After a few years roasting in the fields, a redheaded person might look more like Frankenstein then human. I can’t imagine a redhead in the sun day after day. The skin damage would be horrific.
That leads to a social stigma. It makes them a target for all kinds of rumors.
What was the Sherlock Holmes story about the organization of redheads?
My family carries a redhead gene (my mother and her father were redheads, as are my nephews). My wife was petrified that our kids would turn out redhead, although I never really understood what was wrong with it. As it is she comes from pretty dark-toned Eastern European stock, so our kids never had much chance for anything but dark hair and brown eyes.
“The Red-Headed League.” I’d never really comprehended the variation in shades of red hair until it listed all of them.
I wonder how far spread and back the anti-red sentiment goes. Which societies were afraid of red hair, which ones venerated red hair, and which ones didn’t really care?
The ancient Jews didn’t seem to have a problem with it. Both good and evil Biblical characters (specifically, Esau and King David) were traditionally depicted as redheads.
Sort of personal account: my high school principal was a closet redhead. She told us at a senior event that she wasn’t actually blond. She just couldn’t find a red wig when she married (many religious Jewish women wear wigs when they marry), because back then red was considered ugly or unlucky or something. I remember being as to what was wrong with red hair.
I had recalled reading something about Judas being a redhead, in Googling, I came up with http://jhom.com/topics/color/judas.htm article, which touches on not only that subject, but several other theories of why red hair is seen as bad.
Does this apply to anyone with red hair or just “gingers” who also have really light skin and freckles? From their portraits, Henry VIII, Edward VI, and James I all seem to have had reddish-gold hair, but they also had average-looking complexions that were not particularly pale or freckled.
Fixed your link for you.
The OED includes the following quote:
1610 J. HEALEY in tr. St. Augustine Citie of God XVIII. xii. 677 An order was set downe, that they should sacrifice nothing but redde oxen and red-headed men,…so that Egipt hauing few of those red heads, and other countries many, thence came there a report that Busyris massacred strangers.
I of course have not seen this 1610 translation of The City of God, but I take it that the quoted text is some sort of footnote or commentary on Augustine’s text, which refers to Busyris sacrificing strangers.
Thanks for that, jbaker! That clarifies things enormously. This commentary on Augustine’s reference to Busyris is actually reporting a story from Diodorus Siculus, I.vi.16:
“But, however, it is lawful to sacrifice red oxen, because Typhon seemed to be of that colour, who treacherously murdered Osiris, and was himself put to death by Isis, for the murder of her husband. They report likewise, that antiently men that had red hair, like Typhon, were sacrificed by the kings at the sepulchre of Osiris. And indeed, there are very few Egyptians that are red, but many that are strangers: and hence arose the fable of Busiris’s cruelty towards strangers amongst the Greeks, not that there ever was any king called Busiris; but Osiris’s sepulchre was so called in the Egyptian language.”
I can’t find the Greek text online.
ETA: “Typhon” refers to the Egyptian god Seth, whose red hair was referenced in the article cited by dzeiger. Seth normally has an animal head in Egyptian iconography, but he is traditionally red (all over).
Anyone ever see a redheaded teenage girl that goes to the tanning bed? Not a pretty sight.
Given that racism of various kinds and anti-gay bigotry are so prominent in the US, not just among private company but as tools of political discourse, we often forget how far ahead of the backwards European societies we really are. The idea of the British Barack Obama (someone of Indian ancestry, perhaps) rising to PM at this point is ludicrous. Similarly, yes, it really is the case that you will be shut out of prestigious jobs, marginalized in politics, and perhaps even physically assaulted for having red hair in England. We want to believe that this is all “ironic” or joking because we can’t fathom it being true, but just like the Africans who, to this day, murder people for being “witches,” the British really are that uncivilized. It’s something those of us with the tendency to idealize the “progressive” Europeans need to come to terms with.
What? Based on our treatment of bonfire heads, copper tops, carrot noggins, ginger nuts, or whatever you want to call these hell spawn?