I don't think you understand the math of this. It's not that anyone wants a higher population, it's that the spectrum is a little screwed up. There's this line in the middle (fertility rate 2.1), and anything to the right of that is "population spirals out of control". Then everything to the left of it is "human extinction in just a few centuries".
We're currently on the "human extinction in a few centuries". And all the arguments that we're not are positively stupid. People seem to think that we're like moose on some island, that "population bounces back" (it does for animals, because their fertility rate never goes below replacement, so when population pressures subside, their populations recover). Every time you ask "what's the case for higher population", you're actually helping to murder our entire species.
If you were rational, you'd be pushing the idea that we need that 2.1 fertility rate, the one that doesn't result in higher population, and doesn't result in human extinction.