I understand that what children are supposed to eat is a bone of contention between parents and grandparents in many families. However this is not the main point of my question. I would like to describe a bizarre stalemate situation remotely related to the "proper food" question:

Due to a medical condition my son had (sort of an eccema on a finger) that did not improve my wife suggested to try a cow milk-free diet, or at least keeping cow milk to a minimum. We went ahead with this and things seemed to improve, but then it was Christmas eve and big showers of milk chocolate were to be expected from all sides. So my wife called my parents in advance and kindly asked them not to send milk chocolate this time. My parents seemed to be a bit puzzled by that request, but did not object. Yet.

It was not until a week later that my father called my wife. That's where things are getting complicated. The content of said phone call is being recalled fundamentally differently by both parties. My dad says he just stated his concerns about the measure we took. My wife says, the call was one long stream of accusations, culminating in the claim that not allowing milk was "neurotic". My dad denies to have said that, saying that he stated that the measure "would make our son neurotic".

I talked to my dad, but we could not find a consensus on this issue. He asked me if I had a suggestion on how to proceed. After quite some thinking I suggested to him to call my wife - telling him that I only had second-hand information and apparently could not contribute anything meaningful to this conflict. I asked him twice, but to no avail. He claims not to have done anything wrong.

My wife is not really motivated to approach my dad herself, since I asked her to do this in previous conflicts already, where my dad's response was something along the lines of "gee, what conflict? do we have a conflict here?"

Has anyone had similar experiences where family communication got totally stuck? I'd be happy to learn what your solution was, if any.