Yes, it really does matter. If it's a century off, we'll probably manage it all wrong if we try to manage it now. The longer we can wait to deal with the problem, the more prosperous we'll be when we deal with it and the better the technology we'll have to address it with. Also, the more science we'll know, so our chances of screwing it up will be lower. (Imagine if we invested tens of billions into electric cars and trillions into nuclear power in the 70s because we were told we only had 20 years of oil left.)
The difference between this simplistic silliness and reality is why this kind of reasoning is complete nonsense. It's not about driving SUVs, it's about growing global economies so that we have the resources and understanding to deal with big problems the best way possible.
Every reduction in human population is one less ticket in the lottery for the next Einstein or Beethoven. The stakes are as high as they can be.
There's an old truth saying that the longer you wait the more expensive and hard things will be to change.
Wouldn't it have been great if we'd done that? Invested in electric cars, and nuclear? Then we would probably have an efficient electric car today, and knowledge about nuclear power unknown to us. Perhaps we would use thorium reactors? Perhaps something better?
the electric car was invented before the internal combustion engine driven car. The electric one lost due to real physical disadvantages and economic realities that persist to the present day. So your assumptions are demonstratablely wrong. We also know how to build thorium reactors, we just don't.
I'm all for growing economies. I'm against waste. Be frugal when possible and use resources where it does good. You can achieve the same thing with a different type of car as you can with a SUV. You're just wasting resources by building and driving that. Not that SUVs are the main problem, but they illustrate a point.
The SUV has a valid use case. It's not significantly different than a minivan, nor are they less efficient; and they can be used as a small truck as well.
I'm in total agreement with you about the population thing though. But I have one more thought about that. How do we make sure that the potential Einsteins/Beethovens are able to reach their full potential? How do we equalize the chance everyone gets when starting out their lives?
We can't. The best we can do is to present a level playing field and hope that the law of averages will permit these talented types to rise to their potential.