I believe some brewers use foaming agents to enhance the head.
Then he was descended from Joseph Priestly, because what puts a head on beer is carbonation. 
A-B may make crap-tasting beer (it’s the rice), but they don’t dump garbage into their beers either. Just one more reason to drink craft beer from a local brewery.
Most of those ingredients are pretty straightforward:
Amyloglucosidase is an enzyme of some sort, most likely used in the mash to get the very most starch converted to sugar.
Papain enzyme is a proteolytic enzyme meant to break down protein haze in the beer.
Potassium metabisulfite is likely used in their mash strike water to reduce phenolic flavors from husk material.
Carbon dioxide… they use that for force carbonation, just like almost every large-scale brewer and soft drink maker.
Propylene glycol alginate - that’s your heading agent. Sounds like a fairly innocuous seaweed derivative used for thickening.
All of which are things you can buy at your friendly neighborhood homebrewing store in some form, so it’s hardly like they’re super-secret megabrewer tricks.
Basically you can do all that stuff through careful brewing, but it’s both a lot harder to do, and harder to do consistently. Miller’s not doing much of anything all that weird here. CSPI needs to calm down and go back to whining about chinese food and fast food.
My guess might be something to do with 2 row vs. 6 row barley, if it’s something that’s consistent with the US megabrews, and not with US craft brews or European brews.
Propylene glycol alginate is used as a foam stabilizer, potassium metabisulfite is used for killing off wild yeasts (even by some homebrewers), Emka-malt is some kind of sugar-related agent, judging by a government document I found, might be a food coloring.
Edit: Too slow…
This is the key. It’s not all that hard to brew “naked,” but it’s a bitch to do it consistently, especially at the volumes of product the mega-breweries churn out. Toss in the fact that their beers are so light that there are no flavors to hide behind and you can see where the megas will take advantage of chemical additions wherever possible.
Nice that laws like the (German) Rheinheitsgebot exist…beer should be made with water, malt and hops…only.
I assure you that most of them violate that rule by also adding yeast.
It also eliminates many delicious Belgian varieties which add candi sugar (basically rock candy sugar) to up the alcohol content while giving a lighter body, or coriander and orange peel (essential to many witbeers), honey, or fruits (lambics), not to mention alternate bittering/preserving herbs such as heather or juniper, which were used before hops gained prominence.
It’s a nice law, but it’s not my Law.
Wheat is good in beer. Cinnamon, on occasion, is good in beer. And many other Rheinheitsgebot breaking ingredients.
No yeast?
That’s gonna be interesting.
I fought the Rheinheitsgebot and the Rheinheitsgebot won,
I fought the Rheinheitsgebot and the Rheinheitsgebot won.
And weissbier/Weizen, made with wheat and barley.
Not to mention all those wonderful Combo beers like Orange Wheat and Pumpkin Ale.
I don’t know why brewers insist on putting pumpkin in beer, as it does nothing for it, so far as I can tell. Most of them taste like you dumped a bunch of cinnamon and nutmeg into a perfectly good beer, or the ones with actual pumpkin flavor taste, well, vegetable-y, which is not a flavor I look for in beer.
But, otherwise, I agree with you. If you followed the Rheinheitsgebot, you wouldn’t have a good portion of those wonderful Belgian beers.
The Rheinheitsgebot law was before they knew what yeast was, so it’s not mentioned in the original text. Beer will spontaneously ferment from yeasts that naturally occur on the grain themselves (and in the air, too, to a lesser extent.)
This thread is making me thirsty.
Added in the last 5 min boil.
Incidentally, if you don’t mind beer snobbery, Beer Advocateis a pretty good web site if you want to find out more about beer.