Can you expect people you talk to, to have the same vocabulary, knowledge and worldview as you? Probably not. Should you explain everything like they're a child? Probably not. Should you act incredulous when they don't understand what you're saying, even if it's super obvious? Nope!
A better way to react, is to hide the fact that you're surprised, and instead either move on or explain the concept.
Some of my interactions that I regret the most, have been my acting incredulous. For instance, when I said "here's an easy question" and they couldn't answer it. Or when I showed how sure I was that my counterparts in dialog knew a particular word and they didn't.
As always, there's an xkcd comic succinctly describing the issue at hand.