Africa and Islamic cultures are projected to be the Lions share of pop growth the next 30 years.
Western culture pretty much guarantees curbing population growth is a non starter.
They're saying that in today's Western culture, it's impossible to make an argument for controlling global population expansion because of where that expansion is occuring. Places such as sub-sahara Africa, the Middle East, India. Muslim countries, black countries, for example. That for Western culture today, the view that the wealthy first world is privileged (and should act a certain way accordingly), makes it impossible to confront excessive population growth in less privileged parts of the world, because of guilt, political correctness, or similar.