I'm with the OP, assuming the atmosphere in the store warranted it. Maybe it didn't, given him getting shut down. I always try to be friendly to other patrons in any gun store. Especially with a newbie, I think we're all on trial when they're in a gun store. I'd add that, in my gun-unfriendly area, two of the four stores I frequent are run by crotchety guys who are difficult to approach and take some time to "crack." I've put up with this for years, due to lack of alternatives.
The OP was hardly being a weekend warrior blowhard, which is what we we all find annoying.
I get Sam's point, but when I'm in a store, as I frequently am, where my presence seems to be an inconvenience to the person behind the counter, I'm more concerned with people like the lady in question being comfortable than I am with the owner being even more irritable than he typically is.
I know that many of you come from areas where gun ownership is more common, where you can stroll in to an LGS and grab a cup of coffee and have a conversation (the kinds of stores I'd rather have in my neighborhood, but don't), I'm probably more jealous than disagreeable.