My problem with sales people in general is that seldom will they say " I do not know" and instead will provide inaccurate information. Regardless of the reasons this happens all the time.
The other aspect which is human behavior and most people's morality shifts based on the dollar value involved. You see it with the family squabbles as heirs pick over the bones of a deceased relative's estate and you see it in business and in politics. Some professions put their practitioners more at risk as the dollars at stake are higher.
A sales clerk at Home Depot can provide poor information and the customer is seldom going to risk life or limb or much money as a result. The salesperson at the car or RV dealer never is very knowledgeable about the products they are selling. I know more than they do about the vehicle after reading the manufacturer's brochure.
The salespeople I have known were expert at selling and not at all expert about what it was they were selling whether it was software, computers, bulk commodity products, vehicles, or RV's. They knew how to read people and how to pitch a product and how to overcome objections and set aside concerns. That is very different from knowing a product's attributes and deficiencies and then communicating that information to potential customers.
Surprised that a retired salesperson would have such thin skin. I would expect anyone who has been successful in sales to have learned to shrug off rejection or criticism as it "goes with the territory". Hard for me to invision a whiner being successful in anything.