It is mainly used to criticize the conservative and authoritarian views of parents who are unconditionally treating or assimilation without acknowledging the diversity of autistic people.
A large portion of autistic people, and a fair amount of parents too, believe that funneling a massive proportion of autism-related funding into prevention isn't very helpful for the autistic people who already exist.
Since autism is ingrained into the brain's structure, trying to destroy it in an existing human being might be like letting a bull loose in a china shop. It doesn't sound like a very realistic or safe option. Holding out hope for a cure to swoop in and fix everything sounds like a waste of time to many autistic people. And it may encourage people to turn to pseudoscience when modern science fails them, subjecting autistic people to dangerous experiments.
Basically, it is not possible to give a person a different brain, beacause the brain is the person. Nothing suggests that there would be a "soul", "mind", or any similar, transferrable, immaterial entity.
Since the idea of an actual cure to autism belongs so deeply to the realm of science fiction, people are worried that a "cure" would be nothing but an euphemism for prenatal testing and selective abortion, preventing undesirable fetuses from being born. They'd rather funding go into finding ways to improve the quality of life of autistic people, such as researching helpful therapies, providing better lifetime supports, and finding ways to cure or alleviate common ailments (like anxiety and epilepsy).
Obviously, wasting your energy on hoping for something that 1) no one really even knows what it would actually mean 2) is not going to be even remotely possible within our lifetime or ever at all and 3) even if it did exist, would likely to be devastatingly hampered by all kinds of ethical probelms, is not going to help you or your loved ones. While being on the specturm can be extremely tough – even for many of the so-called "high-functioning" people – there are more realistic social, legal, technological, psychological and even medical accommodaties and remedies that can help autistic persons. For example, if someone has sensory issues related to high-pitched noises, a more realistic solution than trying to alter one's brain to erase the root cause, would be to preprocess the audio input electronically to make it more tolerable. Social and communication issues can be alleviated by promoting acceptance and tolerance and by making blatant cases of discrimination legally punishable. Comorbids, like depression or ADHD are treatable by mainstream medicine.
To sum it up, wallowing in misery and/or subjecting yourself, your children or anyone else to dangerous, pseudomedical experiments conducted by cranks and charlatans is not going to help. The idea of "curing" autism has received much more attention than would be justified by its nonexistent merit. There are much better things to do to help people on the spectrum.
- Autistic Dreams: "Someday My Cure Will Come"
- Vox: Fake autism treatments show the lengths parents will go to "cure" their kids
- Science-Based Medicine: The autism "biomed" movement: Uncontrolled and unethical experimentation on autistic children
- The Guardian: I don't want to be 'cured' of autism, thanks
- The Cut: The Problematic Obsession With 'Curing' Autism
- Autistic Mama: Why Don't Autistics Want a Cure for Autism?
- The Aspergian: The Debate Over an Autism Cure