Well, most new bikes come with brifters, and most advertising features brifters, so it's hard for an uninformed consumer to want anything else.

I wouldn't say they're quite as bad as your shop owner makes out. They do have some advantages, like being easy to shift down on a hard stop for an unexpected red light or left/right cross motorist for urban riders, or easy to shift down while heading uphill while loaded touring. One of the disadvantages nobody seems to talk about is that you're pretty much locked into one hand position (on the hoods) to get those advantages -- sort of takes the benefit of "multiple hand positions" out of dropped bars.

I think it really comes down to personal preference. If someone's buying their first road bike, let them ride it with brifters -- compared to the body position change from a MTB or cruiser, that's small change. Then it becomes a case of what you're used to.