Joining the chorus here. I'm actually appalled at the thought of someone overstepping boundaries and simple courtesy in this way, although as you mentioned, it happens with children sometimes too and we do not get to tell people to leave their kids outside. However, I have and do put limits on what the children do in the house and what parts of the house they are welcome in (like Brooklyn we have a rule about where you can eat in the house) and I will tell children to take their muddy shoes off, etc. and not to tease or bother the cat.
I've had a houseful of children for the past month and one of them had trouble understanding that he should not pull the cat's tail. The cat was incredibly patient and tolerant with him but finally turned around and let him know whose house it was. Fortunately there was no skin broken.