https://www.foodandwine.com/beer/corn-syrup-beer-bud-light-commercial
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"And yet, brewing ferments sugars into alcohol anyway — meaning most light beers end up with little-to-no sugar regardless of what kind of fermentables you put in them. So to imply that corn syrup is somehow worse for you by tacitly tying it into the criticism around high fructose corn syrup as an unhealthy sweetener is entirely misleading."
A different perspective...
For years craft beer brewers have used ingredients as a way to distinguish between their product and mass produced beers. Their audience is aware of the
Reinheitsgebot and it is often viewed as a higher standard, even if the purity laws are are not observed by all brewers all the time. Corn is not an "allowed" ingredient.
Coca Cola has been under fire for using high fructose corn syrup, instead of sugar, in its U.S. products. Mexican Coca Cola (as distinct from Mexican coke) commands a premium when it is available in the U.S. because it uses sugar.
In that context this ad taps into a general perception that, in some cases, corn syrup is "bad" in beverages. It also taps into the craft beer focus on ingredients. It distinguishes Budweiser from its competitors for the consumers who care about these things and one can imagine Budweiser declaring success if a someone who would normally order a craft beer finds none available and orders a Bud (instead of a competitor or just switches to water). Given that all the megabrewers are losing sales to craft beers this could be one way to stem that tide.
Big corn certainly has something to react to but in the context of Bud vs. craft beers, it seems that corn is not the target, just collateral damage, in a marketing war that has been going on for several years.