Hmm, having been in the situation, I know it’s difficult. I try to make my listing as little attractive to people without social skills as I can. It helped, but some pass through the filter regardless. It’s uncomfortable having a cold presence hovering in the other room.
If you know them longer and outside your own home, it’s easier. I consider an autistic neighbor a friend, but it happens that I just leave him in the bistro mid-sentence, even if he invited me to a coffee. What I observed over the years, that just slides off him. He generally expects the worst of everyone, feels obliged to help strangers and friends (not confirmed foes) and at the next meeting, the world starts new, if I start it with a smile. He has absolutely no understanding when he hurts someone a bit or profoundly, but can entertain a group to tears of laughter.
With a guest, you don’t have the time to work that out and no wish to do so.
My strategy is to be friendly at every encounter, just chat on a bit, leave them alone a lot.
If the behaviour is inacceptable, I give simple orders. No explanation, that’s confusing. Like “wipe that dry!” “Shoes off!”
Consider, that he won’t get a reason, another person would get and come to the conclusion to do what a normal person should do. If you said “street dirt makes my white carpet grey”, “spilled water makes the wood rot”, that’s just meaningless information. A moral obligation to make your host happy and not ruin her things, is even farther in the realm of mystery.
So short orders it is. I guess their world inside is very frightening and understandable structure is welcome.
If the conversation is out of line (your line), you could just say “I do not want to talk about that !” And go away, close a door between you. Next meeting you start with a smile and an unrelated topic.
As for the review, there are different possibilities. He won’t get irony, if that’s your choice how to smuggle a warning in.
Or you could stay to bare facts. “X has an astonishing frankness in his conversation, which made me uncomfortable/ ... which I had to learn to handle. “
thinking about it, I had a few guests, where I gave a light / clear / brutal warning and I don’t recommend a hostile thundercloud to my fellow hosts. 😉
my worst case had a perfect prior review. I asked about it: the host relegated him to a nook in the attic, which you would be hard put to call a room. It had a bed and a chair, but was way under the level of an ancient servant’s room. Both were perfectly happy with that arrangement. He did not have any notion how to treat a normal apartment, but no notion either, what minimum standards should apply to the treatment he receives as a paying customer.
