Have you pictured what a society with mostly unproductive humans (relative to AI) and no income redistribution looks like? Peaceful and tranquil aren't words I'd use to describe it.
Neither did I. My argument is we need a long-term population decrease to maintain a stable society if all the wild AI predictions come true. We simply can't have 25% unemployment for multiple generations without something like UBI. And even with UBI there will be lots of idle hands and unrest.
In that sense we're lucky that the AI boom and a trend toward smaller family sizes is happening roughly at the same time.
A halving of the world population is like the world as it was in 1970. Not some Dark Age devoid of prosperity. Getting to that in 2 or 3 generations, in the absence of a climate change calamity, wouldn't be the worst thing.
The population doesn’t just halve. Instead the population ages dramatically.
A threat to what? How can it be that AI is poised to eliminate large numbers of skilled jobs but we still don't have enough humans? Both can't be true simultaneously. One of them has to be a lie.