http://www.answers.com/topic/mental-retardationHe is most definitely a nefarious bastard.
Idiot indicated the greatest degree of mental deficiency, where the mental age is 2 years or less, and the person cannot guard himself against common physical dangers. The term was gradually replaced by the term profound mental retardation.
Imbecile indicated a mental deficiency less extreme than idiocy and not necessarily inherited. It is now usually subdivided into two categories, known as severe mental retardation and moderate mental retardation.
Moron was defined by the American Association for the Study of the Feeble-Minded in 1910, following work by Henry H. Goddard, as the term for an adult with a mental age between eight and twelve; mild mental retardation is now the term for this condition. Alternative definitions of these terms based on IQ were also used. I mean no disrespect to those who are mentally retarded. Just those who use their intellectual gifts to hurt, kill and destroy the innocent.