Except you didn't say the exact opposite.
The topic here isn't whether I personally want treatment; it is whether being autistic is a horrible thing that we should actively prevent anyone from suffering from. And as soon as people who are actually autistic talk about that, we get told that we're "high functioning" and thus don't count, because obviously what's at issue is "severe" autism. So the people who are the closest to having any information that they can relate are discounted.
Thing is, the point about a "spectrum", as opposed to a "continuum", is that it's not all more-severe/less-severe. There are tons of different ways in which the autistic population varies. The assumption that anyone who can write clearly can't possibly have any idea what it's like to have "severe" symptoms is incoherent.
So, recapping the impression your posts create:
1. If someone is autistic, and can't function, that is autism being non-functional. It's never something else that happens to be happening in the same person as autism.
2. If someone can communicate, their autism is "not severe", and they are "high functioning", and thus not entitled to an opinion on what it might be like to be "severely" autistic.
3. If an autistic person has anecdotal evidence, it's just one anecdote and doesn't matter. Your nephew, by contrast, is the gold standard of statistically significant and representative results.
Just seems a little unfair.
Look, I get the desire to have a way to make things better. And I can see the issue when you've got this relative who's incapacitated, and also there's a diagnosis. But it's not at all obvious at the current state of the art in the field that the problem there is autism per se, rather than some other condition, which isn't autism, and if that got treated he might be fine. Or maybe not. We don't know. But handwaving and dismissing people who have real and relevant experience, and telling us that we don't count because we're not "severely" autistic, implies that you do know. That you have all the answers, that you've found definite proof that this really is always and forever just autism, and that fixing it would make it all better.
And that's... Well, first, it's premature, and second, it's an invitation to eradicate all future autistics, of any variety, because no matter how precocious some of us are, we apparently spend a few months, maybe a year or two, not able to talk, and thus not able to decide whether we want to be treated. Or "cured".