Retarded is defined by Google as less advanced in mental, physical, or social development than is usual for one's age, so it's a real word without a disclaimer that it's considered pejorative. However, Wikipedia claims that the word is used less often now (because people are too sensitive) and that it is being replaced by words like special and challenged. My question is, what's so special about being retarded, and isn't challenged insulting, more so than the word retarded? Even the American Association on Mental Retardation didn't change their name because it offended people (they did so because they work with a lot of people who are not mentally retarded.)
The definition of retarded hasn't changed, but apparently everyone wants to sit somewhere on the fringes of being offended because it's cool. I imagine these people get highly upset when DNA tests reveal they have no minority ancestry, but that's just speculation. If I would have referenced special dogs, or challenged dogs, I doubt my point would have gotten across and probably caused confusion instead. I give it another thousand years before we can only use five words from the English language without offending someone.
This dog is no longer challenged.