Not used to dealing with curmudgeons? I can’t speak for all of them, for they are fearfully independent cusses, but I am not offended by much other than blatant stupidity.
You’re not going to do that, even if you try, so don’t worry about it.
Best way to handle it is to let the curmudgeon handle it, without giving clues about what you expect.
When I was in grade school, people would come up to me and thrust some substance under my nose commanding me to “smell this!”
I would look at them with a carefully neutral expression and nod politely, and then say, “Yes, that’s interesting.”
They were always put off by my lack of reaction, but the truth is that I wasn’t smelling what they proffered; I was holding my breath.
It was almost always something noxious or unpleasant. Only very rarely might it be something nice, and then I could simply ask to smell it again.
So being presented with stuff completely at random is something I’ve learned can be disturbing. I like to make up my own mind about things. I should probably start teaching a class about it. The world needs more curmudgeons, doesn’t it?