Thankfully, as an assignor I have the respect of the coaches I assign for. They know I won't entertain any complaint about a call without the play on Hudl and the question/complaint written out on a form developed by others. That simply means no whining.
If, in my opinion, the crew is right or wrong, I say so, and I say why. If the film is inconclusive, I tell them that, too. Sometimes we have to agree to disagree, but they generally appreciate having an ear they can bend. I try to keep it a positive learning experience for the officials. In the interest of full disclosure, my written response goes back to the coach, to the opposing coach, and to the crew.