I’ve only really had experience with A. the car salesman, so I’m reacting to abstractions here, but here goes:
My relationship with the car salesman is always going to be somewhat adversarial. In a sense we kind of depend on each other, but our interests are opposed: he wants as much of my money as he can get, and I want to give him the least possible. That sets up an inevitable conflict, all masked behind a veneer of amiability, and it’s that false friendliness that’s most disturbing and inspires mistrust.
The criminal lawyer will be very manipulative when he needs to be, but I fully recognize that what he does is absolutely vital to the function of justice. Our system depends on having defenders who will spare no effort in mounting a vigorous defense of even the most unsavory people. It may not earn them much esteem from the public, but it serves our collective good. I may not trust the version of facts that they present, but I don’t feel that they’re the adversary in the picture, working against my interests (although I’m sure @john65pennington may see this differently).
As for the milkman, I have absolutely no grounds for either trusting or mistrusting him.