Race is a construct fostered by history and convenience. There is scientifically speaking nothing to the concept of Race. In fact it was the WHO (World health Organization) that recommended dropping race from its queries. What race is- is a set of inherited genes that may or may not depend on each other. The genes for leukemia present at a high rate in the black population has nothing to with the melanism. There are people in parts of china who live in areas with high rates with malaria who pass on and have leukemia at higher rates.
So if I call the collection of inherited autism genes a race it is every bit as valid. The only context you could argue is historical. So Even if you eliminate environmental triggers that may or may not exist the child or adult is still autistic.
I have included an Amazon Link to one of the seminal works in this area below