I think it might have something to do with him "subtly" disclosing (undetected by most people) that he's not coming back next season. That, and maybe just an uncharacteristic (albeit small) F-U to the Goodell establishment, and the fact that Budweiser deserved a prop because they've obviously paid him handsomely over the years to endorse their product.
And it was his stage, for a brief moment... to connect with people who are down-to-earth and don't spend $5 of their income on a bottle of expensive craft beer.
Either way, I don't hold it against him any more than Beyonce dressed like an internet porn actress in the halftime show. (which, btw, I'm not totally against either!)
Much ado about nothing, except maybe the outside notion that it was a subversive hint that he's done playing football.