Who Can Speak for the Spectrum

Very often when an autistic person makes some statement about autism (contradicting what the autism establishment wants to believe) they are told that they 'don't speak for' X category of autistics. I would give a qualified agreement to that.
I know my own mind. I also know the behavior of people I interact with and what they say about themselves or the behavior of other people. I can make inferences from statements and behaviors about another person, but I am not capable of reading their mind. I can't know for certain if my inferences are correct, or if other people's statements are correct. I know intimately what my particular kind of autistic mind is like, but I don't know anyone else's mind, except what they tell me or I infer from their behavior, which is not infalible.
The same applies to everyone else. If you've decided somehow you know what someone else's mind is truly like, then without knowing any more information I can say you are wrong. You know what you observe or what they say. What they say may or may not be accurate, your interpretation of their behavior may or may not be accurate.
My inferences about other people, though fallible, can be useful. I infer from my autistic friend's smiling and flapping and tensing that he is excited, when I ask if he is he replies 'oui' (yes), so I assume he is excited at those times. I don't know that, the way I know if I'm excited or if he's flapping his hands or said yes when I asked if he was excited, but the assumption has so far been verified. People do this all the time - make inferences about other people's mental states from their behavior and what they communicate about their own mental state.
A complicating factor is differences in behavior patterns, mental states and the relationship between them in people with different kinds of minds. Every person is unique in these factors, but everyone has more in common with some people than other people. Some of the statistical outliers have been grouped into various diagnostic groups such as LD, ADHD, autism, OCD, etc, etc, based mostly on behavior with some diagnoses including self-report of mental states (eg OCD obsessions can only be determined by self-report). If these diagnostic categories have any validity at all, they indicate the individuals within one category have more in common, in some aspects, with each other than the general population. This is true even for broad categories like autism. I wrote a post awhile ago about this, called It Really is One Syndrome (scroll down a bit).
Considering all this, a person from a particular diagnostic group who provides information about their internal mental experience and their inferences about what aspects of this may be characteristic of that diagnostic group doesn't represent everyone within that group. But someone who only has observation of behavior or physical measurements to report, without any personal experience as an individual in that diagnostic group, is even less able to represent that diagnostic group. This latter group includes the vast majority of parents and professionals.
In addition, a person's opinion on controversial issues relating to that diagnostic group does not necessarily indicate how useful their statements about that group really are. We must not have the double-standard of accepting what certain people say about a diagnostic group while rejecting other people's statements on grounds that also would, if applied equally to all, reject those we accept. For example, it makes no sense to accept what Temple Grandin says about autism while rejecting what, to choose a random example, Frank Klein says, on the grounds that he is high functiopning and doesn't know what it's like to be low functioning autistic. Both of them are verbal autistics living independendantly and fairly successfully who had a history of speech delay and have, from early childhood, shown significant autistic behavior which continues into adulthood.
[Edit: Is anyone actually reading my blog? The past several posts have had no comments left on them.]