This is all a tempest in a teapot. The FDA is proposing rules for complying with a 2011 law passed by congress to ensure food safety. Brewers had been exempt from the rule because they were able to buy off congresscritters in the past. Now they will have to keep records and conduct training to make sure that they aren't shipping contaminated waste grain to feed cows. People who love to eat cows should welcome the fact that they can be assured that their cows haven't been fed contaminated feed.
All of the hysteria about driving brewers out of business is just hyperbole. Before these rules, brewers could ship contaminated, spoiled grain to feed cows without any accountability. Now they will be accountable to make sure that they don't feed cows garbage... seems reasonable.
You can read the FDA regulation (and avoid the hysterical hype) here:
http://www.fda.gov/Food/Guidan...
I haven't heard of anyone talking about driving brewers out of business wholesale, but any increase in operating cost is going to have negative repercussions for a business, which may mean lower profits, leading to reduced employment. That's just the way these things work. Note that this could also have a ripple effect, such as increasing the price of milk, since farmers have been able to rely on this cheap and nutritious feed for a long time.
You mentioned "they could have" in your response, but I could counter with "they never have so far", which seems a more powerful argument. This practice has been going on for over a century with apparently no real trouble, and suddenly the brewers are going to poison the farmer's cattle? It seems a bit far-fetched, since after all, these are the by-products of human-consumable beverages. I'd be more apt to support this if there was a documented history of problems with this practice.
Government, by it's nature, tends to want to create more and more rules and regulations. I think that's part of the natural desire to proactively protect against problems, but it's also has slightly less noble purposes as well. More regulations essentially means the government has to grow to enforce those regulations. It's in the FDA's own self-interest to pass as many rules and regulations as it can, because then it's "business" grows. That means those in the FDA can move up their own "corporate ladder", so to speak.
Government regulations have to be viewed as a necessary evil. All but the most die-hard libertarians or anarchists would say we need no regulations, but there's always a careful balancing act that must be made between the imposed overhead of these regulations and the benefits they provide in terms of safety, reliability, and consumer rights. So, I think it's worth questioning whether the imposed cost of this new proposal is worth the imposed overhead and costs.