One of the groups thinks of there being "mild autism" and "severe autism" (or "high functioning" and "low functioning"). And they are the ones who want to treat it, and mostly focus on the needs of parents in dealing with their disabled kids.
And then there are the ones I knows more of personally. And they basically think of autism as being a different way of thinking. One which happens to have a common co-morbidity with intellectual disabilities - but the cognitive style and the intelligence issues are separate, they're not two parts of the autism. The first part is the autism, the second just hits a lot of the same people.
And (one of the reasons) the disagreements seem to keep happening because the two sides do not realise that they are conceptualising things so differently. If you think of autism as being both the difference in thinking style _and_ the intellectual disability then the people who talk about how autism isn't a bad thing are clearly detached from reality. And if you think of autism as being a difference in thinking (of which group a higher than normal percentage are also affected by an intellectual disability) then people who want to "cure autism" are basically saying "We want to wipe out your way of thinking".
I don't have an answer for this. And it's not my area of expertise. This is just one thing I've noticed. Please do feel free to point out anything stupid I've said, and I apologise in advance for any offense I've caused.
Original post on Dreamwidth - there are comments there.