Public libraries pay for books they purchase (generally a higher price than retail bookstores) and many governments also have public lending rights that pay royalties per individual borrow.

I never said anything about used books, but they're basically considered a given and not something that can/should be fought in the first place. Used book sales are always going to exist, and have existed since the first books did. Besides, the first buyer counts as a sale, and most used books go through only a handful of readers.

Again, LibGen is great if you're broke and looking for a specific book. Not hating on anyone in that situation. But if you can afford it, or if you're looking for something more general (e.g. "a mystery novel set in the 80's"), then buying new or going to the library/bookstore, respectively, is preferable from the POV of the author.