Earlier quoted context omitted.
What I suspect is true but obviously can't prove: Person with completely healthy brain at age 200 would not be well functioning human being in the society. When we grow we gain experience. That experience shows as habits, perceptions, attitudes and thought trains that makes functioning in the society easy. We learn to see the world trough the past experience. All this turns from asset to liability when society where…
Society would adapt. What's with the contempt for rich people in debates like this? Being mad at rich people for living longer is no less silly than being mad at them for having cars, mobile phones, personal computers back in the day.
The slight increase that wealth currently brings is unfortunate for those who don't benefit from it, but doesn't seem to draw widespread contempt or criticism. It does, and should, act as a spur to remove or mitigate the factors in poorer peoples' lives that stop them from living to the same age.
The 'contempt' in the parent --- pretty mild, and probably not contemptuous enough to accurately be called 'contempt' --- stems from the fact that the rich living much longer than everyone else would be yet another example of widening inequality in society. If we're talking some kind of treatment or technology that doubles lifespan, why shouldn't people be pissed off about not being able to access that? That's not a slight improvement like we're talking about above: that would effectively be an entire second life. I know for a fact that I'd be angry as hell knowing my fiancée would die at half the age of a rich person simply because we don't have the money to buy whatever it takes to make her live to 200+.
The very idea of some people having that whilst others radically and perhaps fatally undermines current human society, which is implicitly built on the idea that everyone only has one life.
It seems implicit in your comment that you think that this kind of imbalance is somehow fair or just or natural. Why shouldn't the aim always be to let everyone benefit from advances rather than just those who can afford it? You can argue that technological progress will allow life-extension to trickle-down, but that doesn't happened evenly or reliably, and seems a bad assumption upon which to base society's progress.