Why are red-haired people called "ginger"?

Correct! It’s not an insult in the context of the quote you gave.

I noticed the Thread, & was interested. No more reason needed than that.

What I do in such cases is simply to subscribe to the thread.

Isn’t that likely to be because the higher incidence of red hair amongst the Scots and Irish (as oppose to the English)?

(missed window)

Just to clarify: isn’t the “ginger” insult in the UK then a form of (or derived from a form of) ethnic slur?

Cartman taught me everything I know about Gingers:

They never sleep. They’re afraid of sunlight. And they have no souls.

Check out white and black rhinos. Madness.

I had always assumed it came from the orange gingernut biscuits e.g. see http://www.ciao.co.uk/Mcvitie_s_Original_Ginger_Nuts__Review_5421945

The Doctor was rather disappointed to find his latest regeneration didn’t make him ginger. “That’s the kind of man I am - rude and not ginger”.

It can be used as a slur against homosexuals (rhyming slang ginger beer = queer)

It doesn’t appear that “ginger” used as an insult in the U.K. has anything to do with insulting the Scots or Irish, since red hair in pretty common in the U.K. Other than the South Park episode, I don’t think I’ve ever heard the term “ginger” used for hair in the U.S. I don’t think that there needs to be any deep reason for a physical characteristic being used by somebody somewhere as an insult. There are insults for people based on their height or weight, for instance. Basically some people will use anything available to have someone to pick on.

I haven’t seen the South Park episode, but (to my mind) it’s interesting that when the term is used as an insult in the UK, the two 'g’s are pronounced in their ‘hard’ form. When used as a spice the 'g’s are usually ‘soft’.

[ul]
Soft form: jin-jer
[/ul]
[ul]
[li]Hard form: gin-ger ( like ‘grin’, without the ‘r’)[/li][/ul]