Do a search for USC communications professor to understand the previous example.

It's hard to defend insulting a person's intelligence, regardless of the word used. A better example would be referring to something inanimate like a company policy as "retarded". Even better is the purging of words like "master" from software. Or actors having to apologize for their Halloween costumes. It seems like every major comedian is complaining bitterly about political correctness lately, save perhaps for certain partisan ones.