> I agree that genetic, pre-natal, and very early childhood environments have a huge impact on behaviour.

I agree, but I don't know why we should have "very early" there. Late childhood and adolescent environments can also have an enormous impact on behaviour.

> My opinion relies heavily on an assumption that there's genetic and pre-natal neurological/gene expression differences for autistic people, and that is probably the source of our disagreement (i.e., nurture vs nature).

There's genetic and pre-natal neurological/gene expression differences for lots of people–yes, including "autistic" people, but also including people with "non-autistic" disorders (such as ADHD, OCD, personality disorders, schizophrenia spectrum, bipolar). I'm unconvinced there is any fundamental difference between "autism" and "non-autistic neurodiversity"–"autism" is a heterogenous collection of many distinct differences, and some individuals with "autism" likely have more in common with certain cases of "non-autistic neurodiversity" than they do with most other cases of "autism". The same difference in gene expression or neuroanatomy can produce radically different behavioural results in different social environments