I constantly correct people in stores... Not sure what the big deal is. Most people thank me for my help. I often direct people to online stores who have better pricing, especially of they do not need it immediately.
If sales people mislead a consumer either on purpose or due to lack of knowledge, why should we not help out. I do pre-sales telecom engineering. I try to make sure I fully understand any technology or product before I start talking about it. I feel my credibility relies on providing accurate information, especially if I want them to come back and use me as a continued resource.
What is the difference?