I agree, that's why I was advocating the mothering approach, or better yet just being their friend. I was working at Goodwill, where most of the employees were mentally ill, and some physically handicapped too. Often the two go together.
The girl was known to lash out at people with not much provocation, so I didn't want to bring up the subject of her leaving in the middle of a sentence. I found with most of the people there, that the best approach was to just be friendly. I would talk to them the same as I would to anyone else, starting with small talk, and slowly progress to see how much deeper they would go. Then you can find certain subjects they are interested in, and go from there. You find that they are not that different from supposedly "normal" people, but just have trouble in areas that affect their interaction with society. "Normal" people have just as many problems, but are able to interact. If you are condescending, or talk "down" to them in any way, they may not react, but they know it on some level. So you treat them like equals, and you find out they ARE equals, but society doesn't understand them. They just have trouble interacting in *normal* ways because society determines what is "normal", and the rules are mostly arbitrary.