We would need to hear his explanation before we could give advice on how to handle it - that way you can hone in on exactly where his flaw in logic/wording was/is. Easiest thing is to blow it off and once you get hired confront him about it.
Best thing you can ever do in a technical interview is admit when you don't know something. I will hire a guy/gal who says they don't know but will research the question over anyone who tries to BS an answer. Technology is incredibly complex and utterly vast. It is impossible to know everything about everything. Its a full time second job just to know a little about a broad array of things.Also, the pres asked me about Crystal Reports which I know nothing about. They were considering implementing it and waned my opinion. I wasn't going to BS them so I said that I had no personal experience with it to be able to take from. I quietly notated during the interview though and I want to be able to give him some more info as part of that email. Since being able to advise on new products moving forward is an attribute they stated they were looking for I think that a short but well thought out opinion in this same email would go a long ways. I think I've got the right audience in this thread for this portion as well so no sense starting a new thread for it. What do you know... good or bad.. that I may include to help make me look better as they make a decision?
As for an opinion on Crystal Reports - it doesnt do anything that you cant do with modern HTML/CSS/AJAX/RoR/etc and O/JDBC connections. It just makes it a little faster (to build) and cleaner (if your not a graphic artist with a background in GUI design) - but it locks you into their product. I am not a reporting monkey but I have spent enough time in databases to know enough to be dangerous. I would still in an interview say I knew nothing about the product.