Let's just make a few corrections.
"Firstly, they bought wholesale at a discount from the publisher, then sold ebooks AT A LOSS to undercut their competitors. This is called "dumping" and, well, the goal was to build a monopoly. "
Amazon sold select titles at a loss, and this is very legal; it is called pricing strategy. Also, saying the goal was to build a monopoly, and only a monopoly, is rather selective in the reasoning. Amazon's other book business (print books) requires a heavy investment in warehousing and shipping. Ebooks require none of those costs, so it would be smart business to make the ebook market as attractive as possible. Lower book prices are one such avenue to make a consumer think about a potential investment in an ebook reader.
"Using DRM on the Kindle platform locked consumers onto the Kindle platform once they bought the cheap books; the goal was clearly to drive competing ebook stores to the wall and then lock the customers in. (The publishers fell for the DRM snake-oil, and thereby played into Amazon's hands; Amazon, not the publishers, held the keys to the DRM.)"
Do you also blame gun manufacturers when someone uses a gun to commit a crime? Amazon may provide the DRM, but the publishers decide whether or not to use it. In fact, because publishers are so Pro-DRM, I'd bet good money that any ebook contract with Amazon required that some manner of DRM be available. And why single out Amazon for having DRM available? Barnes & Noble and Apple both have DRM availability to publishers, who employ it. Your blame of DRM usage is entirely misdirected.
"Secondly, Amazon -- if you read their small print -- claim to be a publishing platform; they are granting the end users a limited license to use their content, not selling the "books" they bought at wholesale consignment price as actual books (to which the First Sale doctrine applies, meaning you're free to do what you like with a dead-tree book you've bought: use it as toilet paper, read it, re-sell it, anything except copy it)."
Once again, you are directing your rant against the wrong party. The publishers control the ultimate license grant, not Amazon, just as Microsoft controls the ultimate license grant to Windows or Office. Amazon has even tried to set up a used eBook marketplace (as did Apple), but the publishers nixed that idea based on court rulings that digital products are licensed, not owned such as a print book or physical disc. You know that ability to "lend" ebooks once? If you look at certain big six titles, you'll notice that it is not enabled. That's because the publisher has a say in the license restrictions.
"In what legal looking-glass world does a retailer get to buy product wholesale for redistribution (the standard book distribution deal) but also get to claim to be a software publisher distributing limited access rights to the product on their platform?"
The one where the publishers granted that right? (see above)
"By 2010, Amazon had about a 90% lock on the ebook market in the USA. That's when the publishers began to panic and look into alternative ways of selling ebooks through other channels that could undermine the AMZN monopoly."
And before that, Sony had a 90% share of the market. You know why? Because no one was in the market other than Sony. Amazon entered an untapped market and pushed their product. Logic dictates that their market share would grow. And it did. But that 90% didn't dissuade B&N from entering the market or Kobo from announcing its intentions to enter the market, all well before agency pricing was a thought in anyone's mind.
"It's a sign of Amazon's huge lobbying muscle that the DoJ anti-trust suit is being directed AT THE PEOPLE WHO TRIED TO BREAK THE MONOPOLY INCUMBENT'S GRIP, rather than at the monopolist."
If you'd have followed this story, you'd know that Connecticut was the first state to push this investigation, and because the red-flag evidence was an across-the-board price increase at all retailers, Amazon was investigated as a possible party to the collusion. But even if Amazon went to the DoJ, so what? If something appears to be illegal, it should be investigated. Why blame the person who alerts the authorities?
Having a monopoly is not illegal, and selling below cost is also not illegal. You need additional acts to make those things illegal. In the case of selling below cost (predatory pricing), you also have to prove that the predator had intentions of recouping costs through above-market pricing once all competitors had been removed. Since Amazon has made a business of selling at low cost, any claim that they intended to recoup costs by increasing prices would be not just speculation, but speculation not based on any past behavior.
That's why that claim fails.
Lastly, breaking Amazon's legal monopoly is fine as long as it is done legally. Collusion is not legal, and if it indeed did happen, the DoJ is right to go after the colluding parties.