It's totally legitimate to favor shorter copyright, but essentially any duration is an arbitrary one. It strikes me as odd that you would be interested in applying the law fairly while also referring to the law as a perversion.
The public did not benefit in any way from its extension. Quite the opposite: every time the duration of copyright terms is extended, the public is robbed of its rights so that corporations which have already made billions off of their copyrighted works can make even more money. When was the last time some copyrighted work entered the public domain? Probably the early 20th century. When people think public domain, what comes to mind is renaissance art and classical music. The truth is everything created in the 80s and before should already be in the public domain and that's very generous, more than enough time for companies to get rich off of their creations.
The original social contract behind copyright was "we'll pretend your intellectual work is scarce for some time so you can profit and then it will enter the public domain". Works aren't entering the public domain because every time Mickey Mouse is about to become public property Disney spends millions lobbying the government in order to extend the copyright duration. Copyright is effectively infinite despite what the law says. So why should the public recognize copyright as legitimate to begin with?
>When was the last time some copyrighted work entered the public domain?
January 1st, 2020: https://en.wikipedia.org/wiki/2020_in_public_domain
I don't know.. I mean yeah, but something strikes me as really wrong about that.
tl;dr: 7-2 as long as there is some type of time limitation, Congress is free to extend copyright terms.
Presumably SCOTUS would say that an effectively-infinite timeline is not "limited" within the Constitutional definition of the word. Eldred v. Ashcroft basically tried to argue that continual decades-long extensions amounted to this, but the Court was not convinced.
This is a good point worth bringing up, since the GP seems to imply it isn't with reference to the wording of the constitution's Copyright Clause.
However, it doesn't answer the moral question of whether congress should have passed that law, or whether congress should pass laws to change copyright term lengths to be shorter. That's not the role of the court.