This whole situation is dumb, from both ends.
AB was dumb to make it, they should have foreseen that they would alienate corn growers and associated communities, which is a hotbed for consumption of their product.
Corn growers being butthurt about this is dumb because the impact is negligible. Domestic beer consumers are pretty loyal, and the few people who actually change brands because of this aren't going to affect the market.
The whole situation is dumb because domestic beer is trash. If you really have to try to sell your trash mass-produced product based on your trash ingredients (or lack of trash ingredients for other trash ingredients, aka rice), you're still selling trash.
Drink real beer. Who cares.