I reckon it's that we've developed a different vernacular, but the words we use are just as disparaging a term(s). Nigger's a very Americanised word and while it's no doubt used the English speaking world over it's not utilised
that much here when wanting to sound racist/shock people. From my own experience, I hear it used in American music and from American comedians, but rarely elsewhere. In the racist times I know about (my parent's generation growing up in the 50s and 60s) terms like wop and wog were bandied about with abandon, they were used on prime time BBC for feck's sake. There's an episode of Fawlty Towers (late 70s show, I think) where the Major refers to black people as 'wogs'. Then came a kind of national embarrassment about it all and it was decreed that those terms were pretty awful and things got banned, like golliwogs. They used to be the logo for Robinson's marmalade and featured in loads of Enid Blyton stories, often, unfortunately, as a perpetrator/instigator of some mischievous toyland crime.
Anywho, they were 'our' words to describe the sort of person people in America would use to describe the sort of person in question and they were definitely more prevalent before the taboos kicked in.
EDITED: 22 May 2015 07:31 by GRAPHITONE