No I agree it’s a poor argument when looked at either extreme. I think most folks would likely agree that some taxation is beneficial, albeit not a 100% tax rate, which would be broadly analogous to the argument that copyright shouldn’t exist.
The person you replied to wasn't making the argument that copyright shouldn't exist. Their argument is in line with "some taxation" where it goes into the public domain after a while, and they only (potentially) called extended copyright terms stealing from the public domain.
