Ms. Manners Nonplussed

Evan has a friend visiting, and said friend has an autism diagnosis which includes the inherent lack of social skills. The young man in question walks through our front door, looks around our home, and states, "I see you have IKEA dormitory furniture. You are low on money. That explains why you don't have much house." *choke* Immediate internal response (which is thankfully not voiced), "Excuse me?! You don't get invited over a second time often do you?" My inner warning bell tolls "AU child. He has no idea the offense given." I choose to herd the dogs to our bedroom to pen them up so they do not bother our young guest. I also gain a moment to pull my jaw off the floor and regain what normally passes for composure. Don finds my discombobulation concerning until it is explained. Then it is merely funny to him.
The boys want to play video games. Evan only has one controller because he has left his at a friend's house that the boys have in common. There is discussion on using the other friend's controller when he is not present. Apparently there is some gamer etiquette of which I am unaware. The boys eventually settle the issue by using the other kids' controller with a pair of our batteries. Maybe the etiquette has to do with the batteries rather the controller? I don't plan to delve too deeply into this one. I am still smarting a teeny bit from my prior encounter with this kid's manners.
In another hour I can send this little darling home. An hour is an awfully long time. Miss Manners failed to write a section on this particular sort of situation, but I am going to assume it is covered under not pointing out our guest's lapse to him. Unfortunately, as a parent, I will be pointing out said lapse to Evan to discourage him from making a similar observation at a later date in a similar situation. That will also require telling him not to correct the friend regarding today's little comment. The social skills do not come naturally to these lovies, but once taught can be assumed with a legalistic rigidity that becomes an issue in itself.