I agree entirely with the article and the point of it and all the wonderful breastfeeding stuff and I'm sure that he's a lovely man, and I know some phrases are in greater use on the other side of the Atlantic, but...
Mental Retardation is the term in current use in the US for Learning Disability (there learning disability means dyslexia etc).
I do literature searches on learning disability topics for my work and was quite shocked to come across it as the Subject Heading in use in the literature but it's the current and accepted descriptive term there for impaired intellectual and adaptive functioning.
I still think there's a big difference between saying that someone is "affected by mental retardation", or even saying that someone is "mentally retarded" (I regularly read a blog by a US woman who occasionally refers to her clearly much-loved brother, who has some form of congenital learning disability, as her "retarded brother") so that doesn't cause me as much shock as it once did, at least when it comes from a North American source) and calling someone "a mental retard", though.
I suppose it just came as a huge shock in the middle of an interesting article on breastfeeding.