I actually know the history of the word retarded as applied to children with developmental delays. Around 1960 clinicians started using the word to label children with delays. And it took about 3 years for children to start using it as an insult.
The bad thing is what these people are doing isn't depriving the English language of a slur. They're actually turning words into a slurs. And depriving the language of words with perfectly innocuous meanings.
I think most people are fine with a style guide discouraging "retards". That's not the issue here at all, and I'm really surprised that you think this is what people are objecting to. Do you really believe this is the problem?
On the other hand, a style guide discouraging "users" or "master" is a problem, especially for a school that offers Masters of Science degrees -- how exactly is their website supposed to cover that? How are software usage guides supposed to be posted online if "user" is not allowed? Or "submit"?
People turn to the web for information and need to be able to obtain this information. Stanford should understand this.
