One child, more children... Right or Wrong???

When Mao announced the baby boom in China it really was well, um, a boom. 5-6 children per couple= the decreasing of resources and increasing of population. After Mao's death the rule of one child per couple was enforced. People obviously would go against it, to prevent such circumstances the government also tagged in that there was a fine if the policy was broken. With that also came the rule that disabled people weren't allowed to get married, and if the first child was a female the couple could have a second child and if that one was a female too then they had to put her for adoption. The preference of a male over a female doesn't just happen in China but also in India where they let the female babies die on their own. Is this policy just?
China already consists of almost 20% of the world’s total population and if this policy was not enforced the population would be double of what it is now. The biggest problem, however, would be the resources and the future of the children. They would not have enough food, water and other things for a person to stay alive. After all it was China’s fault for the baby boom. Shocking, that by 2020 30 million men would not have a chance to get married or have their own child, because of the imbalance of gender. How is this fair for them if it was their countries fault?