@Latte31: As a person who lives with this, I can only say that preconceived notions about people like me are the bane of my existence.
I find that it's more of the environment than the person dealing with this challenge that determines the outcome. My family, for instance, has moved to a rural area, so I don't have to deal with the cacophony of having too many people around me at any given time, and it does help. We strive to live a simple life, with as few complications as possible. This has also helped the family in general, as we have had the time and energy to develop better relationships with our kids. Being removed from the 'average' lifestyle, or 'dropping out' as the hippies used to say, has had many unexpected blessings for which we are truly grateful.
While individual cases vary, I would say that the assumptions you present about isolation and unpredictability, again, relate more to environment than the people themselves. Lots of folks are "unpredictable and can develop anger with not much prodding." Haven't you read the news over the last few decades or so? I see this having more to do with the level of stress everyone deals with day to day in our 'modern' society, not any mental health challenges.
The ratio of horrific crimes committed by 'regular' people shows that the majority who murder spouses, children, random strangers, etc., are not mentally impaired (at least in the traditional/legal sense, although there is something vastly wrong with them to have been able to perpetrate said crimes, period).
You cannot deal with people as 'groups' rather than individuals or those 'preconceived notions' bite us all. Becoming 'educated' about something is much more than reading it in an article or a book, life has to be experienced to be understood.
My grandmother taught me to never judge a person till you've tried walking a mile in their shoes. Words to live by, if you want to live as a human being and not as a mindless robot.