Some of what you're talking about strikes me as a potential disconnect between what is in-character and what is out-of-character. For example, the players making cracks about the guy hiring them, them going about doing their planning, etc. All of that being viewed (by the players) as OOC actions that doesn't represent what is actually happening, or being filtered mentally to be "my character is doing planning and being all professional."
So then, when you respond to those actions, viewing all of it as IN-Character, their response is "well what's his problem?"
It might not be like that, though. I would suggest discussing your concerns with the group. Simply stating outright "hey, last time when you guys did {X,Y,Z} it was really insulting to Mr. J, it was really unprofessional. That's why he told you off there, and was mad."
There really might be a misunderstanding about what they thought happened and what you think happened, so starting off the conversation with clarifying that is probably best so that you're all on the same page. It might not work 100%, and they might be fully aware of what they did and not care. But at least then you know what you're dealing with...