https://www.scientificamerican.com/article/china-says-its-ge...
https://www.cia.gov/library/publications/the-world-factbook/...
Not simply a cultural preference but a rational economic one as the odds a man will earn more than women has quite the better odds, and given their circumstances (and motivation to improve them) people are willing to compromise on the matter. Which is not simply the result of some conspiratorial patriarchal cultural phenomenon (although I'm sure that plays a role as it has elsewhere) but rather something amplified in developing countries where low tech labour and farm jobs are more common than knowledge/service work, favouring the physical attributes of men.
The changing economic incentives will address the gender inbalances faster than some government child policy or cultural/ideological shift...
That being said, one could substitute China -> America and, gender -> wealth, unmarried -> jobless, and I think the accusation would be similar. I've had Americans seriously tell me that the country is on the brink of civil war, which seems about as bad as anything that could come from China's gender imbalance. I'd link that to economic problems, it is the explanation that makes the most sense to me.
Basically, there is a real concern; but I'm not sure it is an /unacceptable/ outcome of the One Child Policy. It might just be an outcome. The OCP can easily be cast as a policy of courage and prudence; overpopulation carries a real threat of starvation and collapse if it overshoots what the local resources can support.
It's probably not a good idea to make value judgments based on the predictions of people obsessed with hysterical political news sources by companies who have make a living selling the public a worldview divided on stark black/white us vs them tribal lines. Where every minor bit of inane news coming out of Washington is blown up into big stories to fuel some grand political drama that never ends.
Meanwhile the world IRL for the vast majority has hardly changed at all in any significant way.
https://en.wikipedia.org/wiki/List_of_countries_by_income_eq...
https://en.wikipedia.org/wiki/List_of_countries_by_distribut...
Wealth, not income. Although I do now see the data is 2000 era, so the situation might be different now. China was a very equal country by wealth back then, though.
The problem is a social preference for sons over daughters.
What should happen is that the families of women are given money and houses by their daughter's husbands. Then girls will be seen as more of an investment than boys, and more families - particularly poor ones - will selectively abort males instead of females. Already this is playing out in China.
Unfortunately this also becomes a problem in the West, because migrants from countries like India are predominantly male, and Indian mothers are still selectively aborting females even when they move to countries like the UK.