Well, I didn't think he made a mistake. I wondered WTF he meant by a discrete camera but I went with it. After all, every single camera* is discrete! Then when he described something "discreet" I didn't realize it.

So don't apologize. Thanks for being there. I [obviously] think there's nothing wrong in helping people express themselves correctly.

For instance,
A discrete bellboy says "I'm working here by myself."
A discreet bellboy would never say to a woman "isn't that your husband over there with that blond?"

*that's actually a joke