Ofcourse mentally retarded people should be considered human. Just because there is a disparity between their mind and their bodies, (i.e. the cause of their retardation) does not mean that every other aspect of them is not human. I once knew a man in Zimbabwe, who appeared very retarded. He was badly squint, badly pigeon toed and his hands back to front. But mentally he was quite sound, yet everyone thought he was retarded. He even practised as a journeyman in mechanics and could diagnose problems better than normal people. One must not forget the human soul. Remember that blind lady, what was her name again, not Marie Curie emmmmm that deaf dumb and blind lady emmmmm, the one that used to clap her teacher. You know the one they made a film about emmmmmm Enid Blyton no Helen Keller, that's it. She could describe a country scene yet she was totally deaf, dumb and blind. So ofcourse we who know how she was able to do so, know that her mind escaped from her body because of her intense desire to see, hear and speak. Because the soul which contains the mind is not impaired she was able to discern all that she could not see physically. So her MIND was not retarded as many people thought in her early years.