It's wrong for merchants to deceive customers.
Peter is selling used appliances and has some customers looking at a dishwasher that he knows doesn't work properly.
Peter wants to make the sale.
Peter admits that the dishwasher has issues and offers to give the customers a large enough discount to cover repairs.
Peter tells the customers that the dishwasher works great and guarantees they'll like it.
The customers are grateful for the offer, buy the dishwasher, and become loyal customers of Peter's.
The customers find out that the dishwasher doesn't work later that night and leave Peter a terrible Yelp review.