People should tell the truth.
Dave is a car salesman and is showing cars to a customer.
Dave wants to sell a car to the customer.
Dave tells the customer the good and the bad about the car and details how much the bad would cost to fix.
Dave tells the customer the good things about a particular car and downplays or avoids the bad things about it.
The customer finds a car that only needs a few repairs, buys it, and is very happy for Dave's honesty.
The customer buys the car, is dissatisfied, and hates car salesmen from that day on.