Malthus was very concerned about unchecked population growth.
Explanation:
As a matter of opinion, I think it would be safe to say that Thomas Malthus would be in favor of the one-child policy because it would be a limit to the exponential growth in population we have undergone since his time. He was worried about our rapid growth in population and not being able to sistaine resources. He famously proposed 2 ways to keep our population in check, by means of "moral restraint" which China's policy would fall under or by means of natural plagues, famine various disease and even warfare.
