What does your DH makes of his father's outburst?.
Your relationship with these people already has a lot of problems in it, this is just one of many others. FIL has not himself explained exactly why his DIL has upset him, he has not told her at all what she is supposed to have said or done. He has just dropped a verbal bomb on her knowing it would cut to the chase.
Re your comment:-
"Do I love him bringing all his own food and utensils to the house because he doesn't like my cooking. No I hate it and think it is rude. Don't tell him that? No. Dh has each time they come repeated please don't bring anything dw and I have planned and will cater. He ignores us and we suck it up rather than cause a scene!"
Ah the old sucking it up/doormat behaviour does not work I am sorry to say. So is it ok for me then to bring my own stuff over to your house, of course not but you tolerated this from FIL all the same. What if you people had turned up with your own kitchen stuff in their house, they would not have liked it at all would they?. You would not have tolerated any of this from a friend, family are actually no different.
You seem nice and reasonable, unfortunately you are dealing with a person who is not and has likely never been reasonable. Therefore you are tying yourself up in knots unnecessarily. He knows exactly what he has said to you and it was designed to hurt you. I would also keep the children away from someone like him as well.
You state yourself that FIL has no health issues and I doubt very much that there is anything wrong with him physically at all. I can just imagine how suggesting that he visits the GP would go, and no it would not go at all well.
You have no recollection of doing this simply because you did not do anything to upset him, its all in FILs head and this is a further example of his own nasty persona.
You people need nice and healthy role models to be around, not ones like his FIL who has thrown a spiteful hissy fit to get you into line.