As I said, slang is understandable as calling another person and I understand the feelings behind it.
Just clarifying that it is a clinical term still in use by physicians and therapists. My
late wife Sarah was an Occupational Therapist who started her career working in group homes for mentally handicapped adults. She cringed having to write the term in her notes, but from a clinical standpoint it is a word that is used to convey the type and severity of said handicap.