He can eat corn just fine, but HFCS gives him a migraine. I'm not sure why, but it happens consistently even when we don't notice it on the ingredients list at first so it's not psychosomatic or anything like that.
I have a cousin who's allergic to peanuts, let's ban those, too. Oh, and a family member who's allergic to milk (lactose intolerance). So, let's get rid of milk.
Oh, and actually another cousin is anorexic, so can we just get rid of all food? I have a great feeling about this!
Peanuts and dairy are usually possible to spot without checking the ingredients list, and they serve a distinct culinary purpose. They have valid reasons to exist, and are fairly simple, if a little annoying, to avoid.
HFCS does not serve a distinct culinary purpose (it's pretty much just sugar but it benefits from corn subsidies), and is impossible to identify without careful scrutiny because it's included in all sorts of foods that it has no business being in. The (purely financial) benefit it provides is far outweighed by its harm to public health.