I don’t, it’s important to clearly differentiate between patents and copyrights, and parent’s example was discussing patents and not copyrights in the context of a discussion purely about copyrights. The reason patent terms are shorter is because patent inventions are considered more important to release into society in a timely manner than works of art. It makes plenty of sense that the business case for music and books and other individual personal or creative works might often take much longer than for, say, industrial corporations. There are hardly any solo inventors actively getting patents compared to the vast number of people creating music and art.

> Shouldn’t the system of intellectual property be the thing that needs to justify itself

It already is justified, and the article re-iterated those justifications while arguing clumsily (IMO) for shorter terms. I’m not debating whether we should have copyrights. I’m just exploring and curious about how to justify any given balance point, and how to reason more clearly about terms. It’s not that easy, and can’t be as quickly stated as many many people seem to assume. People are just throwing around numbers that “feel” good to them, not because they’re aware of the history of media and IP and the many varied problems and experiences people have had.