We need more time to deal with finite resources and pollution. A larger population would decrease the time we would have to find solutions. Even if most of the current world population lived sustainably, we would still need 2.5 earths to support the current population size indefinitely. I believe that we need about 6.5 earths at the moment.

Maybe if we had off world colonies this would be a good opinion, but this blog post is just a bad argument