I suspect there is a strain of anti-Chinese sentiments here. When you see articles relating to black social issues, they immediately get flagged, but articles like these always get through.
We moderate HN to mitigate the worst aspects of this, but there's no hope of eliminating it. HN is controlled by its community. All that moderation can do is adjust the margins.
I suppose macro trends would also explain why black social issues always get flagged on HN as well.