I have some thoughts on the use of the word "retard." I worked for two years doing direct care at a group home for developmentally disabled adults. I can say that when the word pops up (on TV, movies, out in public...) and they hear it, it does hurt. As a result, if you work in that environment, that particular word gains a great deal of stigma and power. It's like Lenny Bruce said, a bad word actually gains power from its being repressed.
I would sometimes find myself feeling the need to say it out loud. Most of the people I worked with talked about this too. It's a hard job and with all the frustrations that build up, sometimes when you're away from work and away from the residents, you just wanna scream about how these "f***ing retards" are driving you crazy. In my opinion, this does not take anything away from the fact that you care about these people. It's just a matter of venting something that builds up. I don't think it's a bad thing to use the word, but you should always be careful about how and when. Many people are very sensitive about it, not just mentally disabled people themselves, but family members and people who work with developmental disabilities.