The liberal consensus is that the careless and flippant use of words such as "fruitcake" and "wacko" reveals a disrespectful ignorance towards people with mental health problems. The Guardian's own in-house style guide counsels against using such "clearly offensive and unacceptable expressions as loony, maniac, nutter, psycho and schizo". But if you want to talk about mental incapacity in English you will not find yourself lost for words. This is one of the richest areas of our language, and we seem to revel in the joyful creativity of coining words that skip around, compartmentalise and poke fun at the serious issue of mental illness.
ENA1 - Language & Representation
Another social group for your answers on ENA1, perhaps?