Is it level one autism or is it extreme dysfunctional doesn't-even-fit-into-society-and-can-totally-tell-he's-autistic autism? I personally think who cares? Someone can say please or thank you if he wants. Then again what option do you have if he is being rude? You can't rightfully go tell a parent how to raise their kid, and you can't go and teach a kid to say please and thank you yourself. Maybe the kid is just a healthy cynic and he feels that saying thank you shouldn't be an explicate rule. In that case I would be thanking the kid for not falling into the trap of social norms.