Copyright infringement is theft because it denies a copyright owner the ability to sell the product for which they have the copyright and thus they lose money.
Thanks for the nostalgia! I remember when people tried to claim that with a straight face back in the 80s, but no one believed it even then. Can you imagine that someone actually said that ridiculous crap in seriousness once? I'm glad we've moved past those ludicrously mind-bending contortions and can laugh about them now, knowing full well that no one actually thinks that way anymore.