The corn growers aren’t upset about this because they think people switching beer brands will impact the market. They are upset with it because the commercial pushes a false narrative that corn syrup is bad for you and products made without corn syrup are superior to those with corn syrup.
i disagree. i think the narrative they are trying to push is that Bud Light doesn't have to add extra ingredients besides the brewing basics to create their beer. normally, adding a sweetener to your beer is either because you're making a particular sweet style of beer or you need to feed the yeast extra to boost alcohol content beyond normal amounts (e.g. the honey added to Hopslam). the other cheap light beers having to add corn syrup seems to be some kind of cheating or shortcut to me. i don't care if the sugars are mostly digested by the yeast or not. the "bad for you" view of the narrative is mostly projection, IMHO.
the true issue with HFCS isn't that it's different than sugar, but that it's so damn easy and cheap to add to processed foods that it's leading to a large extra caloric burden in most people's diets. i try to avoid items that have no or less added sugar (regardless of source) when i can.