By saying “vaccines don’t cause autism”, you are leaving it open to say that “this thing you don’t want for your child, autism, is not a consequence of vaccinating your child”.
It devalues autistic lives.
To people who already prefer dead children over autistic children.
Antivaxxers believe that autism is a defect. Saying “vaccines don’t cause autism, here’s proof!” doesn’t address that they hate autistic people.
Science alone does not address ableism. Because guess who is often in positions of power to decide what’s science and what’s not? Abled people, both physically and mentally. Abled perspectives skew science. White perspectives skew science. Perisex binary cis perspectives skew science.
So yes, vaccines do not cause autism. That lie has been debunked over and over again.
But it doesn’t debunk the lie that autistic people are defective and worthless.