"population is an asset rather than liability comment ?

It depends On my what aspect you're looking at it from. According to the theories of population growth and resources, Malthus theory states that population growth will cause resources to deplete to a point where resources (earths carrying capacity) are unable to support the population resulting in the Malthusian crisis. When the crisis happens, there will be positive checks in place such as droughts an famines to lower the population until a sustainable number for resource usage. This is supported by many Neo Malthusian theories aka modern interpretations but one main fact is that this was said in the 18 century and back then it was simply an agrarian society.

Hence there was boserup's theory which was based on necessity is the Mother of invention ( I think I got this quote wrong) and that basically when population growth increase there will be more technology and improvements to society to increase resources available for usage. Which is largely supported by the high dependence on agriculture in agriculture and technological advancements over the years such as the green revolution and industrial revolution,

Ultimately I support Malthusian theory as it makes sense that no matter what, population will always be a liability in terms of resource usage.