It means: Bad people also have close friends, and good people also have people who regard them as enemies.
It is customary to think that Cao Cao is a villain and a traitor; Guan Gong is a positive character, symbolizing loyalty. As the saying goes: Birds of a feather flock together, and people divide into groups. Good and bad are just the feelings between giving and receiving. There is no absolute good or bad people. Everyone's understanding of the word friend is different because of their different positions and perspectives.
Extended information
Antonym expression
1. Those who are close to vermilion are red, and those who are close to ink are black.
It comes from "The Proverbs of the Prince and the Young Master" written by a Jin Dynasty writer.
Interpretation: Those who rely on cinnabar become red, those who rely on ink become black. It is a metaphor that getting close to good people will make you become good, and getting close to bad people will make you become bad. A person living in a good environment will be affected by good things, and living in a bad environment will also be affected by bad effects. It emphasizes the impact of environment on people.
2. Birds of a feather flock together and people divide into groups.
From "Warring States Policy Qi Ce III" compiled by Liu Xiang of the Western Han Dynasty.
Interpretation: It is a metaphor that similar things often gather together, like-minded people gather in groups, and otherwise they separate. Similar things gather together, and people form groups according to their character and hobbies. Good people always make friends with good people, and bad people always get together with bad people.
3. Virtue is never alone, it must have neighbors.
It comes from "The Analects of Confucius·Liren" written by Confucius and his disciples during the Spring and Autumn Period.
Interpretation: A moral person will never be alone. There must be like-minded people to accompany him. The distance between like-minded people may be very close or far away in time and space, but no matter whether they are near or far, they will eventually have a mutual resonance.