That's the weird thing. Even if you think the plumber is stone wrong, a bit of business sense should tell you to politely acquiesce and move on.
Instead, they demonize this guy and selectively address his complaints. It seems they really can't grasp they idea that not everyone agrees with their sense of what's good and right. And that makes me think issues of ethics never crossed their minds; it looks as though they cannot imagine themselves as being wrong.