The problem is total amount of emitted CO2. A large extent of it being emitted by a rather reduced fraction of the total population (rich countries).
Seems rational to exerce change of this reduced fraction. Indian or Pakistani are respecting their share in terms of emissions in order for climate increase to stay under 2 degrees. We are not, so we need to change that.
When you say "we", policy that can affect carbon emissions and even population trends to some degree are usually made on a country level. So it makes sense for highly emitting countries to reduce their emissions, not for them to be able to purchase "share" by encouraging population growth.
Seems rational to exerce change of this reduced fraction. Indian or Pakistani are respecting their share in terms of emissions in order for climate increase to stay under 2 degrees. We are not, so we need to change that.