I know, and so do A LOT of people, including virtually all shelters. I'm probably weird that I don't consider it as much of an issue. But then again, I also live by the maxim: It's as much of an issue as you make it.
Our dogs are NOT allowed to be messed with when they eat, regardless. We expect the same from them when WE eat. As it happens, they are both excellent around food and I CAN remove any item from them without issues.
I think this particular issue has arisen from lack of structure. Provide the structure and that's half the battle. It may also be that the dog has learned a successful way to ward people off food that he wants or wants to keep - that part I would tackle with positive training and NILIF.
To me, it's natural to guard resources. Perhaps not ACCEPTABLE (dog + teeth + kid = tragedy) but natural, even in a dog who is NOT a) probably hungry virtually ALL the time and b) lacking of any kind of structure or consistency in his life, like the one in the OP.
"Give a man a fire and he's warm for a day, but set fire to him and he's warm for the rest of his life." (Pratchett, Jingo)
"I used to look at [my dog] Smokey and think, 'If you were a little smarter you could tell me what you were thinking,' and he'd look at me like he was saying, 'If you were a little smarter, I wouldn't have to.'" - Fred Jungclaus