In my experience "the rules of social engagement" are as often used to entangle and obstruct as they are to create civility. Think of "foot-in-the-door" phenomenon.

Sometimes rudeness is respect, especially if it's an honest communication.

Jobs needed an on-time supplier, and it was arguably worth the cost of a legal battle in order to get one.

As others have said, though, it spawns imitators that think "Steve berated his employees, so I can too."