I don't think anyone said it was easy... but here's a situation for you..
Coach... "What is that flag for, there is nothing in the rule book that prohibits that" (whatever it may be)
No sir it isn't, but Rogers Redding released a bulletin in 2008, you may not have seen it, in that bulletin he said that this was a foul.
Coach... 
Hard to tell them to "reference the rule book" when the rule book doesn't even have "everything" in it...
Also hard to say that the coaches on the Rules Committee make the rules, but then on the side the Rules Editor releases his own take on one thing or the other and that becomes a silent rule that isn't in the book, and likely hasn't been vetted by the Rules Committee.
These situations are rare, but it is interesting...
By what you write, it sounds as though you worry or care about what a coach thinks. If you've done your job in studying and knowing the rules and their approved interpretations, and applying that knowledge correctly on the field, you owe the coach nothing more than a report of what was called. You do not owe him a an explanation as to where you obtained your knowledge. If he needs/wants education regarding rules, he can approach the appropriate educator/interpreter at a more appropriate time. If you are in a TV break or something and have time, fine. But, otherwise, in the middle of a game ain't the appropriate time. Just tell him, respectfully, "Coach, I've reported the (foul/ruling) to you. At the next time-out, I can try to explain it to you, if you'd like. But, right now, I've got to focus and concentrate on the next play." And then you move on. At the next break, approach him, and see if he wants to listen to you. If so, tell him that the Sec-Ed issues interpretations bulletins from time-to-time, which are available to ANYONE via the NCAA web site, and the ruling made on the field was directed by one of the bulletins. When (not "if") he starts to argue, then you just tell him that he asked a question and you've given him the answer; and, if he doesn't believe you, you can't help him. Move on.
We all just need to know and do our job and not worry about what coaches think.