Well, DavetG, to my mind, never mind the ethical, think of the practical.
A percentage of the CDs/tapes/LPs that I've copied have played well for a number of times, and then the sound has deteriorated. Sometimes into a total mess.
I don't know why, but it isn't because I'm doing it on one particular burner, -I've owned four, all bought new, and it isn't because I've used a particular brand of disk nor a specific burning program.
I've also had harddrives crap out and lost copies that way.
I don't think that this problem is just me. I've also bought, from the artists, self produced CDs which have descended into a hammering noise, and another where the silver recording surface bubbled off the disk.
I'm not unlucky in every aspect of my life. I got a new cartridge for the phono and the LPs play perfectly, even the very first one I bought, sixty years ago.