No I agree, I have Crohn's disease, and through that I know people who have Celiac as well. I understand how harmful that can be to you. If they wanted to have these ingredients in their fries, they wouldn't be poisoning people, though.
The problem is you had an assurance that it didn't, and it is heinous that they would mislead people. I'm not excusing them or downplaying your suffering at all. I think the implication here for some people may be, though, that this stuff shouldn't be in food at all. That McDonald's is wrong to sell anything but gluten-free fries.
Instead this is a matter of a false statement concerning the ingredients. It isn't the gluten, it is the claim of the product being gluten-free. That's why I think maybe the poison thing doesn't ring true, even figuratively.
If you think restaurants should be forced to remove gluten from their food, that's a different matter entirely.