I was chatting with another mom who has an autistic son and she was explaining to me the challenges she's been having with her son's rudeness. He'll walk up to people and tell them they have bad breath or a stain on their clothes or that their hair looks "weird" or any number of off-putting personal comments. His sister has been bearing the brunt of it.
She has been trying to explain to him over and over that these comments are inappropriate, that it doesn't matter if they're true, that they hurt people's feelings. But his counter argument is "Mom, you tell me things like that all the time."
It's true. We do tell our children things we'd never dream of telling a stranger or friend. (My parents still think it's appropriate to tell me to move the litterbox and that I should really weed my lawn on a regular basis.) We tell them that they can't wear a shirt in public which has a giant stain or a series of holes down the front, even if it's their favourite.
How do we explain that social boundary to a child who doesn't get it? What is the real difference, beyond "because I said so"? If we draw the boundary around family, then the sister will still be a target. If we stick with not doing it because it hurts people's feelings, then why is okay for the parents to do it?
It's a real puzzler, and one I don't have a ready answer for. The closest I can come to is in the delivery. There are gentle ways to alert someone to a potentially embarrassing situation. Maybe set up strict guidelines of what it is appropriate to comment on (it might be okay to gently tell someone they have a coffee stain on their tie but it's never okay to tell someone their hair looks weird).
The situation is likely to take several weeks, if not months, to resolve. And the exceptions are going to overwhelm whatever general rule is put in place, because they always do.