You want the discuss the etymology of offensive words?
It's an individual response. Different words mean different things, there are certain words that are wide spread and understood to be hugely offensive, such as the 'n' word, or '****' is it not seen as offensive in the middle east too as a 'general' derogatory way of describing people from that ~area.
'n' word, has as far was used to mean 'black' as in skin colour when referring to someone. ('Neger) It's had negative connotations since ~1500's, when it was used to referred to negatively to black people. It could be seen from an almost, sympathetic view that the 'black' people inflicted bad things upon white people. If that makes any sense. It's only recently ~1900 + that it's being used as a neutral or positive word, but that's in regards to within the black community.
I'm not sure what you want to discuss to be honest?
Words can offensive, they mean different things to different ~groups of people. The 'n' has always really had a history certainly in western speaking words as being a derogatory term for African people. Regional dialects / non standard dialects must play a part too, grouped in with how different 'people', 'groups' of people view and react to words.
No, you mis understand me, disabled people have been treated badly in the past due to their actual disability, same with African people because of their skin colour. With in regards to calling someone fat V racial slur, it would be down to the individual? no? If the second word is the 'b' word, is that not a negative term for a child out of wedlock and was a insult on it's own?
Moses, drop me an email via trust. I'm happy to talk about words. Waay off topic.