My strategy in situations like that is to try to get rid of all respect for the person. If to be offended you have to care, at least on some level, about what the person thinks then demoting them from "agent" to "complicated part of the environment" should reduce your reaction to them. You don't get offended when your computer gives you weird error messages.

Now this itself would probably be offensive to the person (just about the ultimate in thinking of them as low status), so it might not work as well when you have to interact with then often enough for them to notice. But especially for infrequent interactions and one time interactions I find this to be a good way to get through potentially offensive situations.