Population control does nothing to promote a free society or free markets. Somebody already made that bet for you, and you lost.
The bet was made in 1980 between biologist Paul Ehrlich and economist Paul Simon. Ehrlich, the author of The Population Bomb, believed that increasing population would bring disaster and perhaps extinction for the human race. Simon, an economist, reasoned that people are an asset, not a liability. They bet $1,000 on the prices of five common, but vital, raw materials such as grain and oil. If they became scarce, as Ehrlich predicted, the prices would rise. After ten years the prices of all five materials had dropped. Population was not the problem. Though there were more people, resources were more abundant. People were using or producing them more efficiently.
Where would you rather live-- North or South Korea? Its not population that matters, but freedom. Free people produce more and better goods and more wealth, and wealthy nations treat the environment well.
As far as being separate activities, you may be right, though the two are sometimes tied together. Both result in fewer children from the poor. Both stem from a humanistic belief that some people (usually people that look different from us and live in a different part of town) shouldn't be a burden on the rest of us.
http://www.pop.org