English is not my native language, but it was interesting watching the hoopla over the use of the R word, first by Rahm Emanuel as an 'insult', then by Rush Limbaugh as 'satire', then by Sarah Palin's differentiation between the two, and finally by Stephen Colbert's play on the same.
A lot of words that are now used as insults did not start that way. Retard means slow. Mental retardation is quite literally translated into the benign mental slowing, which seems to be a perfectly fine lay-term for cognitive impairment. After being bandied about as an insult for several years, it is now rightly considered a pejorative term. There is talk of replacing the DSM diagnosis of Mental Retardation with Intellectual Disability. Will that stop words for low intelligence being used as derogatory terms? Remember Idiot? And Moron? All words for people with different grades of IQ before they passed into the world of bad words. So how long before Intellectually Disabled becomes the new good bad word?
We could extend the argument further, to the historically hurtful N word. I heard it on M.A.S.H. a couple of weeks ago, being thrown around casually to describe a blood dyscrasia more common in African Americans. No doctor in his/her right mind would dare do that today. How about Native? Midget? And one of psychiatry's very own, Borderline? I've already heard it being used as an insult, though mostly by psychiatrists and psych patients.
We're never going to stop insulting each other and making fun of the vulnerable. Maybe that's how it will always be, a few words chosen to segregate and divide, until they fall out of favor, to be replaced by new ones.