Welcome to our forum.
My take on the conversation...He (the "doctor") was in fact the owner of brand x spa cover manufacturer, and became offended at the notion that you didn't know about his product, or didn't care enough to consider them competition, thus no need to research his product, hence the indignation.
is it my responsibility, obligation, or even wise business practices, to know EVERY OTHER brand of cover out there?
He was rather irate and asked if I thought it was the customers responsibility to gather information and make the comparison.