"Fifty steps mocks a hundred steps" comes from Mencius, King Hui of Liang, Part I. Mencius used the analogy of deserters on a battlefield: two soldiers fled in defeat, one ran fifty steps and the other ran a hundred steps, and the one who ran fifty steps mocked the one who ran a hundred steps for being cowardly. In reality, both were deserters, essentially the same, differing only in degree. The deeper meaning of this idiom is: when one has the same shortcoming or mistake as others, only slightly less severe, yet ridicules others without any self-awareness. It is often used to criticize those who see only others' faults while ignoring the same problems in themselves, carrying a sarcastic and derogatory tone. In cultural background, it embodies the Confucian ideas of self-reflection and putting oneself in another's place, reminding people not to apply double standards. It is mostly used in scenarios where someone points out that when a person criticizes others, they have similar flaws themselves, or for self-deprecatingly acknowledging that both parties are equally matched. Emotionally, it often carries teasing, sarcasm, or helplessness, and the tone can be light or heavy.
📝 Example
You always say Xiao Li loves being late, but you yourself often clock in just on time too—isn't that the pot calling the kettle black? (Satirizing someone who mocks others for having the same flaw, only to a different degree.)
Both companies illegally discharge wastewater; the one that discharges less criticizes the other—that's truly the pot calling the kettle black. (A metaphor for two sides being essentially the same, where the one with the lesser offense has no right to criticize the one with the greater offense.)