Enh, I see what you're saying but I don't know that I agree - I don't think a lie always has to be intentional. Any falsehood can be construed as a lie, intentional or not.
You've got a group of people telling another group of people that something they are experiencing isn't actually there. That they're making it up. It "sounds" to me an awful lot like...
Person A: "I feel sick when I eat foods that contain gluten."
Person B: "You're just making it up. This study proves it."
Anyway. I think we're into the realm of semantics now anyway. Ultimately, I agree that in general, most folks (here and elsewhere) aren't trying to be malicious.
Back to the broader topic, this article is a good read - it seems quite evenhanded, from what I can tell:
Is Gluten Sensitivity Real?