It is theft, but the argument is better framed as to whether or not it's moral theft. Most people who pirate feel comfortable pirating from larger corporations over small time creators/groups, with the usual justifications you've provided above. Personally, I've justified it at times because I couldn't afford to purchase the thing, which leads to another argument of "if I wasn't going to buy it in the first place, is it actually effecting them".

There is no argument to be made, however, where it isn't true that if you were to have purchased it, the owner of the idea will make more off of it. Whether you care or not about that owner getting more is a different argument, but you are robbing them of value for the idea, however little that value might have been.

I'm not arguing for or against pirating, but people in the comments saying it isn't theivery really seem to be arguing whether stealing is wrong or not. Call it what it is and go back to the argument people have been having for thousands of years.

Which, I realize I didn't address libraries. Taxes pay for libraries to operate, and then the library pays to have copies of the works. If no one wants to read my book, libraries aren't going to just go out and buy thousands of copies. And trying to tackle libraries would also start to erode arguments for reselling something. And to bring it back to the OP, I've read books in a library before that I enjoyed enough to purchase a copy of my own. I've also read books I haven't. But someone purchased that book for me to rent, and in a small part, I've paid for that book myself by paying taxes.