As the mother of an autistic son, I can see how people already burdened with their own lives can have a hard time understanding autistic behavior. I also know that the only real socialization a lot of kids get is in their neighborhoods. Since autistic people are basically born without the social gene, they need all the normal behavior modelling and socialization they can get. When social behaviors including social speech must be learned, the more heard and seen the better.
Plus, evidently, the autistic kid's dad is an insulting neanderthal who shouldn't be talking to his new neighbors the way he has talked to you.
And, your son has been endangered.
so
I would suggest going to the school and suggesting integration lessons, an understanding of autism issues being discussed with faculty and a plan whereby neighborhood and other school parents can get together and share the joys of knowledgeable socialization. The dad (and mom, if she exists) will see that everyone cares about integrating the boy, that there are methods and ground rules, and by bringing a buncha people wishing well into the mix, there will be a forum to discuss some of the outrageous behaviors that the dad has exhibited and work on how the community is going to be part of a solution, not an exclusion.
Meanwhile, is there an open door, open yard policy for every other neighborhood kid except the autistic one? Hopefully, you so not comprise a whole neighborhood, i.e. there are other folks you can get together with to share the integration?