You're mixing up several things, all of which actually boil down to the fair use exceptions I was mentioning.

Making copies of a book you legally own for personal use is an established fair use exception to copyright. However, making copies of a book that you borrowed from a library would be copyright infringement. Similarly, lending the copies you've made of a book to friends would technically void the fair use exception for your copies.

The copy that a playback device has to make of a copyrighted audio/video file for its basic functioning is typically mentioned explicitly in the license you buy, thus being an authorized copy for a specific purpose. If you make several copies of a file on your own system for personal use, then again you are likely within fair use exemptions, similar to copying a book case - though this is often a bit more complicated legally by the fact that you don't own a copy but a license to use the work in various ways, and some companies' licenses can theoretically prohibit even archival copies, which in turn may or may not be legal in various jurisdictions.

But in no jurisdiction is it legal to, for example, go with a portable photocopy machine into a bookstore and make copies of books you find in there, even if they are only for personal use: you first have to legally acquire an authorized copy from the rights holder. All other exemptions apply to what you do with that legally obtained copy.

This even means that you don't have any rights to use a fraudulent copy of a work, even if you legitimately believed you were obtaining a legal copy. For example, say a library legally bought a book from a shady bookstore that, unbeknownst to them, was selling counterfeit copies of a book. If the copyright holder finds out, they can legally force the library to pay them to continue offering this book, or to destroy it otherwise, along with any archival copies that they had made of this book. The library can of course seek to obtain reparations from the store that sold them the illegal copy, but they can't refuse to pay the legal copyright holder.

> I love how enthusiastic this post is while being wrong.

This is a very funny thing to say given that post is entirely correct, while you are wrong.

> Making a copy of a thing does not violate copyright

Yes it does, unless it's permitted under a designated copyright exemption by local law. For instance, you mention that the video player makes a copy from disk to memory, well that is explicitly permitted by Article 5(1) of the Copyright Directive 2001 in the EU as a use that is "temporary, transient or incidental and an integral and essential part of a technological process", as otherwise it would be illegal as by default, any action to copy is a breach of copyright. That's literally where the word comes from.

> If I own a license to listen to Metallica - Enter Sandman.m4a that I bought on iTunes and in the download folder I screw up and I make

> Metallica - Enter Sandman(1).m4a

> Metallica - Enter Sandman(2).m4a

> Metallica - Enter Sandman(3).m4a

In legal terms you do indeed owe him something, yes. It would probably be covered under the private copy exemptions in some EU territories, but only on the basis that blank media is taxed to pay rightsholders a royalty for these actions under the relevant collective management associations.