If a historian says that The Jungle is factual, then he should be able to cite facts and would not need to cite a novel. It's really poor scholarship to cite a novel as a factual source. There's no way to tell what parts of it are factual and what are "artistic license". The book has neither footnotes nor references.
I own probably close to a thousand history books, and no, history books are not written as novels. They do tend to tell a story, and they sometimes have an agenda, but they all have footnotes and references where there facts came from, and they make it possible for the reader to distinguish the verifiable facts from the historian's opinion.
> Are you, a Libertarian, proposing that the government spend years and millions of dollars creating a U.S. official definition of "juice" for labeling purposes?
The government does now. I don't see a problem with it, nor anything unlibertarian about it.
> What happens when inevitably companies skirt the line?
They get charged with fraud.
> What if I'm a company that produces milk but I cut corners and possibly some number of milk products happen to be poisonous, though I never try to poison anything?
That's called negligent homicide. There's nothing libertarian about condoning negligent homicide. No libertarian suggests that nobody will commit crimes under a free market.
And so on for your other examples.
> the freedom to do all of the above with even more impunity than they do now.
I'm afraid you've been misinformed.
To give an example of regulations that libertarians would oppose - rent control.
If you want to impugn capitalism, may I suggest "The Robber Barons" by Josephson. Josephson seems to share your viewpoint, and he wrote an actual history book of capitalism of the period, complete with an index, sources, quotations, footnotes, all the good stuff. I have complaints with his conclusions, and I think he cherry-picked his facts to fit his viewpoint, but you'd be on much more solid ground than with Sinclair.
Your examples sure are clean. But the real world is dirty. What exactly is "juice?" Are you, a Libertarian, proposing that the government spend years and millions of dollars creating a U.S. official definition of "juice" for labeling purposes? What happens when inevitably companies skirt the line?
And sure if I sell you poison on purpose knowing it's poison wanting to kill you that's murder. What if I'm a company that produces milk but I cut corners and possibly some number of milk products happen to be poisonous, though I never try to poison anything? What if I build cars and realize they will explode and kill people but figure I'll make more money selling them and dealing with the deaths than a recall? What if I use my vast power and wealth to systematically suppress all knowledge about how dangerous my products are and market them as safe and "doctor-approved", watching my smoking customers die thousand after thousand? What if I sell investments I know are bad, but I lie and fake ratings for them and sell them as high-quality, defrauding people by the millions? What if I extort an entire state by manipulating its energy supply? What if I poison rivers, drinking water, give communities cancer, lie about emission test results and poison the air, create children's toys with lead all because it's more efficient? All of these examples I cited have happened, recently, in our currently non-Libertarian society, and are nearly identical to your example and nobody was charged with murder. Libertarians support fewer regulations, less oversight, more market freedom -- the freedom to do all of the above with even more impunity than they do now.