NO respectable craft brewer in America or elsewhere would use rice or corn in their beer. ZERO.
Craft beer is about quality. The reason it DOES matter if beer is mass produced is because the quality sometimes takes a back seat to profits. Traditionally, corn and rice are used because they are cheaper and more readily available than higher quality grains which are supposed to be in beer.
When a large conglomerate purchases a craft brewer or a quality European brewer, there is concern that the quality of that brewer may go down as the corporation tries to reduce costs. Obviously whether or not that happens varies by each situation.
Nobody here is arguing that Bud, Miller or Coors is better than Carlsberg or Paulaner. We're saying American craft beer is better than ANYTHING these large corporations can create, because they care more about quality than cutting costs.
To tie this back to WDW for a moment, this point is relevant because Disney frequently uses "craft" like Lagunitas, Goose Island and Golden Road which have been bought by larger brewers and are no longer craft. That's why, prior to the price increase, I always tried to purchase local Florida brews (from craft breweries like Cigar City) when in the parks.