What philosophical truth does the fable of self-harm illustrate?

There is such a dialogue in the TV series "My brother is Shun Liu":

The Japanese general asked Wu Dabala, an officer of the puppet army, "I saw a sign on the wall of the war zone, which said that China would not fight China. What do you think? " Wu Shuo: "China people have beaten China people for thousands of years, and the imperial army has come to save us!" " "

The ancients said that brothers were cowards and were humiliated outside, which was really naive.

The Book of Songs came into being in the pre-Qin period, when people were simple and could not foresee the long history. People in China are too smart, but they are smart in the wrong place and like to fight with each other. Therefore, one of the experiences of political struggle summarized by China people is to make friends far away and attack near.

Li Shimin was just a king. After the Xuanwumen mutiny, he killed his brother and younger brother and put his father under house arrest before he ascended the throne.

In the * * * dispute between the two countries, both sides pulled in foreign aid, seemingly nibbling at each other, but in fact they were all seeking their own interests, and they all just used the strategy of making friends far and attacking near.

So don't be fooled by the cruel sight of cannibalism. People who do this are not stupid. In the final analysis, every man for himself, the devil takes the hindmost.