Earlier quoted context omitted.
The set of celiacs is much smaller than the set of people who think eating gluten free food is a good idea.
Afaik unhealthy diet increases gluten sensitivity. I have it and it sucks having your knees and elbows hurt for a week after eating a gluten rich pizza.
I don't want to argue with your overall point at all, because I assume that whatever this sentence specifically means to you is true for you - but given that there is no actually objective definition of what a healthy diet is - it's hard to agree with the statement in general. I would feel like I was eating unhealthily if I had a can of coke every day, but that doesn't actually mean it's unhealthy. It probably depends on everything else I'm eating, how much I'm burning off, maybe even something as fine-grained as how fast I drink it. You would almost definitely feel unhealthy if you were eating bread every day, but as long as it was whole-wheat and had some good sandwich fixins in it, I'd feel pretty good about that.
Anyway, sorry if I'm being pedantic, but I feel like people toss around things like "healthy diet" as if we're all supposed to know and agree what that means.